So there should never be a situation where realizing your desires might be facilitated by dishonourable action?
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You would like the Holy Avenger longsword. It would give you mechanical benefits. It is held by your superior, although if he were out of the picture, you would be the likely inheritor of the weapon in question, a relic of your order, as you would be the most likely to be chosen to succeed him. That fellow is currently in a bit of trouble with the Order. You have stumbled upon a clue that might lead to his exoneration. You can ignore the clue, or follow up on it.
Sweeping it under the carpet likely gets you a mechanical advantage in the form of the Sword and the increase in rank in your order. Doing the honourable thing - proving his innocence - does not. Mechanical advantage gained from dishonourable behaviour.
I don't see how the above really relates to what I said, which was that when I play an honourable warrior answering a divine calling I want to have as much meaningful (= desired) impact on the fiction as the other players.
The example you give, for instance, seems to equate the PCs desires with those of the player (after all it is the PC's action which is dishonourable, presumably - I assume you're not asking whether I would lie to or betray the friends with whom I play the game).
But the example also rests on certain assumptions such as that my PC won't get a holy avenger longsword except by the path you describe. That might be so in your game, but why would I play a game like that? The edition of D&D I run is 4e, where item acquisition is on a level-based rationing, and whether I do the honourable or the dishonourable thing has no bearing on how many XP I earn.
you have emerged from a secret door in the midst of battle. A great enemy has his back to you as he battles another opponent. Do you slip up behind him for a Flanking bonus, or call out "Face me, Blackguard" so he can position himself where he cannot be flanked?
I don't know - put me in the situation and let's find out. If it's a dragon, I'd probably flank it. I don't see that dragons are entitled to a fair duel. If it was a hobgoblin war chief I might not flank.
The 4e paladin has various powers intended to support the paladin in soloing in various ways, so that not flanking is not necessarily a mechanical disadvantage.
So is this only an issue when the Power doing the judging is acknowledged as Good?
I'm not 100% sure what the "this" referes to, but the issue of the GM superintending the players' evaluative judgements becomes particularly acute when the "power" doing the judging is a moral exemplar, yes. I hoped I had made that clear some hundreds of posts ago.
I also hope I've made it clear that the player in the example I posted didn't think that his PC was doing the right thing by Vecna's lights. He knew he was opposing Vecna, and Vecna's interests, and Vecna's desires. I forced him to choose between the Raven Queen and Vecna - a choice I do not believe he was that surprised to have forced upon him - and he chose. He wasn't surprised that Vecna then punished him by shutting down his imp.
The player could, of course, have chosen Vecna. The Raven Queen would then not have had any immediate means of punishing the PC; and at least in the immediate term, the other PCs probably wouldn't have noticed. The player deliberately took the risk of suffering punishment, to which he knew he was exposed - he had deliberately implanted the Eye in the imp to bring Vecna into play as a counterbalancing force against Levistus - because in the play of his PC he had an evaluative response. There are some resemblances here to player wanting his/her paladin to fall.
He has all the same options? Where is the Familiar his class abilities grant him? Where are the benefits of his magical loot, the Eye of Vecna? They were taken from him, and in a manner someone above noted was outside the action resolution mechanics.
They were not taken outside the action resolution mechanics. They were taken as part of the resolution of a skill challenge. Furthermore, it is inherent in a 4e familiar that it may be shut down. And it is inherent in a 4e artefact like the Eye of Vecna that it is somewhat overpowered but also potentially temperamental.
The key issue for me is that the player's evaluative judgement is not invalidated, nor even called into question, in the episode of play I described.
In choosing to play a Paladin, the player has chosen a character who must either live up to the ideals of his Exemplar or fall. That's the contract he, the player, made by choosing the class with those rules. That really doesn't seem that difficult a concept from where I sit.
What contract? With whom? Are you talking about the player or the PC? My players don't enter into any contract with me. And paladins don't enter into a contract with the divine, at least as I conceive of them. They are not Faust; they are Joan of Arc.
Of course they must live up to certain ideals or fall, but that doesn't tell us anything about who adjudicates that matter in the course of play.
I find that if people are aware their actions are under a microscope, they will behave differently, without full autonomy. Further, the pressure may "lock them up". I don't want that with people I trust to both be sincere in their play and be provocative and dynamic (coherently) when responding to adversity.
This is a good description of my own play experiences and play preferences.