Wait. Did I use sappy or soppy in that original poll question?
I’m not going to try for a comprehensive definition of nobility of spirit here, since part of the fun is seeing how each fantasy author works it out. I will emphasize, briefly, that I’m not talking about bloodline. “Nobility” in this rant refers solely to character traits. (And to my picture of those character traits. Obviously).

1) Keep it consistent.

Fantasy is threaded with loopholes. The oath that otherwise guarantees awful consequences for the protagonist is thwarted by its own wording. An insignificant amulet turns out to be just the powerful weapon the heroine needs. The villain neglects to watch the hero’s sidekick, who stabs him in the back (while somehow avoiding all the other guards and traps in the chamber).
How well these work tends to depend on individual situation and level of writing ability—except, I think, where nobility is concerned. Nobility stems from principles, usually commingled with or identical to honor, duty, morality, and other codes of behavior. If a character breaks his code and remains noble in the reader’s eyes, he does it through service to a higher principle, such as love, or he chooses to follow one part of the code over another, or he chooses his personal beliefs over formalized ones. I think it’s deeply and intrinsically damaging when the author introduces a loophole that will let the character do whatever he wants and yet still get away with claiming “nobility.”
Examples of these:

  • The character does something illegal, but when he gets back to the capital or the place where he’ll be put on trial, the government has passed a law declaring the illegal behavior all right.
  • He chooses to save a character’s life over another, dying person’s, and then finds out later that the dying person was already dead.
  • He does something that dishonors him in most friends’ eyes, but at the end of the story they run up, throw their arms around him, and declare that they never stopped believing in him and all is forgiven.
  • He lives by his principles right up until the moment he needs to defeat his enemy. Then the Wise Old Mentor or another authority figure explain that that’s okay, because, after all, the enemy was an enemy—never mind what they said earlier in the story about even enemies not being outside noble treatment. (See point 4).

For me, it’s very, very hard to claim a character is noble when he’s a hypocrite. He may not have chosen to be so, but if events have made him so and that’s still all right, then I suspect the author of once again loving her protagonist too much to let him make a mistake or even a hard decision. He must always be right. If he doesn’t know he’s right, then the permission to be so is granted retroactively.
Truly noble characters are the ones who stick by their principles and don’t break them without anguish and hard decisions, or the principles don’t mean jack squat.

2) Introduce cruelty.

Most noble decisions in fantasy are presented in the light of tenderness and compassion. The noble character is the one who offers mercy to his defeated enemy, who forgives the most horrible injustices done to him, who finds a compromise that pleases everybody instead of alienating one side or the other. It’s not really hard to make these decisions. They are not cruel. They benefit everyone and punish no one.
But what happens if the noble decision and the compassionate decision are not the same thing? More, what if sparing the enemy or forgiving the injustice or making the compromise means that there will be further danger in the future, and to other people than the protagonist? He can choose to be cavalier with his own life in the name of his principles. Will he be so cavalier with others’?
The most concise example here is that of a noble leader who wants to spare his enemy’s life because he surrendered. On the other hand, spare the enemy and he’ll probably just go back to his evil old ways. On the off chance he doesn’t, his own enemies will hunt him down out of fear. He’s done too much to be forgiven by anyone who doesn’t share the leader’s strict code of honor. And the leader’s own code and the law call for the criminal to be punished for his crimes. Only the fact that he surrendered argues otherwise.
Is the leader really going to just let the criminal walk free? Gods, I hope not. Or at least not without a lot of soul-searching on the leader’s part and genuine repentance on the criminal’s part. Someone who releases a criminal on compassion and “trust in his innate goodness” is ultimately stupid, not noble, and I bet the author just wanted me to read a scene where the hero’s enemy is overcome by his compassion and falls down sobbing, at which point (you guessed it) we’re back to sappiness. And that’s ignoring the carryover from point 1, that it’s betraying the hero’s own principles of compassion and care for others. Does the criminal’s freedom mean more than the lives of all the people he might hurt, then, or more than his own life, if his enemies might hunt him down? Will the hero really make others suffer just so that he can exercise his compassion?
Some sharpness, some actual ethical minewalking, would be useful here. The hero who spares his enemy’s life because the enemy has repented and the hero doesn’t want vengeance anyway is following his own desires, without so much as catching an ethical grenade.

3) Vary the arena.

It’s pretty easy to be noble when you’re a lone figure riding out to face the villain, or standing on a dais above a crowd and giving a speech, or standing on a balcony and looking in tortured silence over moonlit mountains, or whispering in the dark that you’ve just decided to hunt down the man who murdered your parents. It’s harder to be noble on a day when sunlight pours through the windows and you’re one among a small number of people at a party and they’ve just offered you the throne, speaking in earnest voices, and you think they may have shady ideas but you’re not sure.
If a noble character is only noble because her surroundings do half or three-fourths of the work for her, something is fucking wrong. Learn how to portray the quality in calm weather, in calm scenes, when the character is alone, when she’s with friends, when she’s facing enemies, when she’s within easy reach of an army. Learn how to do it with high places and low, and with hard decisions and easy ones. Learn how to show her principles working together at all times, not just when you want to remind the reader that, “Yeah, hi, noble protagonist over here.” I’ve gotten character whiplash before when the heroine acts like a not-particularly-savory mercenary most of the book, only to suddenly grow rhetorical skills and a master’s degree in ethics when she has to give a speech.

4) Show how the principles flow beyond the character and the people he immediately cares about.

Some of those people can certainly be his enemies, which is where the “honorable enemies” conceits come in and start leading the narrative down the road to sappiness (especially if the hero psychoanalyzes the villain and persuades him to relent not by nobility but by power of love). It would be even more impressive, however, if the principles applied to more people than that, if the protagonist was shown as a truly noble person living in a world where everyone, even the characters who don’t matter to most fantasy narratives, is portrayed as mattering.
Someone truly noble in spirit, I think, wouldn’t assume that someone didn’t matter just because he once gave her friend an evil look, or because he was a servant, or because he was a citizen of a neighboring kingdom. And the more powerful the truly noble person is, the bigger that circle of caring extends. I won’t call it “compassion”; I already demonstrated the problem I have when the narrative equates a noble person with a compassionate one. But a noble person ruling a kingdom will have many more people who matter to her than one who knows only her village and the people in it. And though her friends and family and lovers will understandably rank higher in her eyes than a stranger, I think she would consider the strangers as no less important or human (elven, whatever).
I can accept a fantasy where the heroine assigns her friend to rule over a certain section of the country as long as that heroine isn’t presented as noble. If she is, then I want to know why she didn’t think about who would actually make the best ruler. Does her friend come from that part of the country? Is he popular there? Can she trust him to do what she wants and what is right without breathing down his neck every moment? Is she appointing him because it’s the noble thing to do, or because she’s really grateful to him? If she’s grateful, and his appointment would hurt the people he’d be ruling, surely she could find some other way to reward him.
The heroine prizes honor, dignity, intelligence, and the intrinsic worth of the human spirit, does she? Then demonstrate her prizing them in everyone, not discounting some people as unworthy of notice or automatically forgiving her friends their lack.

5) Appearance and birth and magic should only be used to accent an already noble personality, not in replacement of it.

Does the hero have an aquiline nose? Well, okay, we could always use one. Does he walk with his head high and meet everyone’s eyes? Come on in. Was he born to a rich family? Then perhaps he doesn’t drop the silver on the carpet when he eats at the high table. Does he have magic that can only be used by “the noble and pure of heart?”
Stop right there.
This one right here would explain why so many of the fantasies I enjoy are the ones where the characters have really flexible codes of morality and live by them as best they can (Martin, Kay, Pratchett), or do what they think is right, ba-da-bing, the end (Green, Brust, Butcher). At least they’re bloody consistent, and not pretending to be noble because they look or act or fight a certain way. It also explains why retold fairy tales and I generally do not get along.
It’s hard to keep up the standard of nobility I’ve outlined above, especially when authors are used to wielding appearance and aristocracy and magic to make their characters noble by default. There are damn few ugly fantasy protagonists, or plain ones. Many protagonists are openly aristocrats, are secretly aristocrats, or ascend to aristocracy by the end of the story and are better at it than those born to the position. Many have magic that can’t be used for evil purposes (die, soppy healers, die!) or that, though it could be, never tempts them.
I’m not so much irritated by this as baffled. I sit and stare at these characters for a while, and then I go away.
When you can have noble people like the ones I outlined in the first four points, why would you want to use beauty and birth and battle-magic as more than grace notes?

6) When the character demonstrates his/her nobility, you can use other emotional demonstrations than tears.

This goes back in the direction of sappiness, which I think got lost somewhere along the way. If a noble person pardons his enemy, or grants a petition, or agrees to give a possible traitor a second chance, the person really can do something other than fall to the ground weeping. For some characters, it’s going to be appropriate. For others, it’s really, really not. Besides, where come the tears, there comes the purple language, and the single tear, and stupid symbolic nonsense about tears renewing the earth (how? They’re salty!), and all the rest of it.
So consider whether the recipients of the noble character’s good graces wouldn’t clasp hands instead, or suddenly hug him, or whisper a few words, or accept it with a lifted eyebrow and a nod that says, “I knew you’d do this all along, you didn’t fool me.” These are harder to make all about love and rainbows and fluffy pink kittens.

7) Nobility should probably run alongside self-knowledge.

You might have an “instinctively” noble person. You might also have a story that makes me want to vomit on your shoes.
Self-knowing protagonists are, surprise, surprise, rare in fantasy, despite all the introspection that protagonists get up to. Either self-knowledge becomes something that the character is supposed to grow into, rather than having at the beginning or along the way, or the authors want to keep the character ignorant of his own reactions and beliefs because they want him to plausibly say lines like, “He felt the strangest attraction to her and he didn’t know why.”
I prefer self-knowing characters. I prefer characters who can sit themselves down and admit mistakes, apologize without being forced into it, debate their noble principles internally and make an informed decision instead of a sudden one that just happens to be right, and have a rich and complex inner life. Not surprisingly, I also think these characters make the best noble people.

8) At the ending of a noble character’s story, head for glory instead of comfort, for joy instead of humor.

Lately I’ve encountered a plague of fantasy short stories that trip themselves up at the end because the author just could not wait to launch a “clever” line or a platitude. And if this follows the character’s noble action, then there goes the nobility like air out a punctured balloon. If the author mocks his character’s nobility in narrative, as opposed to letting the character mock himself or his enemies go after him, why should I believe he was ever noble or that I should take it seriously? And if he says something like “Love conquers all” that I’ve heard a thousand thousand characters say a thousand thousand times before, why should I believe that he’s made a hard or principled decision? He’s tumbling back into platitudes. That’s not a good sign.
If you want to maintain an environment that’s conducive to enhancing a noble character’s nobility, then I think glory—stern and resolute and sharp as the decision or action that the character took—is better than one filled with homilies. And if you want to show the character being happy, the gladness or joy he’s found will be better than humor. (Why, yes, I do consider humor and happiness to be different things, or there wouldn’t be a difference between rants where I yell bitchily and rants where I burble on about what I see fantasy as capable of achieving).
I don’t see nobility as ponderous. I do see it as careful. Give me a chance to laugh with your characters, and I’ll do so happily. But give me a chance to laugh at them, and I’ll wonder why I need to be invested in their nobility, or whether I should take anything in the story seriously at all.
I will leave you with a Simon R. Green quote, from Winner Take All, and characters who never made a fuss about nobility one way or the other:

Hawk: “That was a nice punch of yours, Isobel.”
Fisher: “My strength is as the strength of ten, because my heart is pure.”
Hawk: “And because you wear a knuckle-duster under your glove.”