First of all, I don't have a preference for simple, whatever you mean by that. Second of all, the Paladin had many options other than saying "Ok." At least one option was mentioned to result in both people surviving.
No, we're told that the DM intended other options, but that's different from what was apparent to the player. It would be like providing the trolley problem but not telling anyone there's a third option available where they can pick a third track with no one on it. You cannot hold someone accountable for not guessing a hidden option is available. The offer from a very powerful dragon that the paladin has no hope to defeat was leave and live or stay and die -- either way the NPC is eaten. Holding the player responsible for failing to guess that, this time, the powerful and lethal dragon could be stared down is not a valid position.
It's quite simple, I determine how my character feels, the GM determines the results. I might delude myself into thinking I am doing the right thing, as enumerable bad-guys in fiction and reality have done, but that doesn't mean I am still good. I might convince myself that I am still honouring a contract when I clearly am not. People are able to convince themselves, at least (especially) for a limited time, that they are doing "the right thing" even when they aren't. So like I said, it really depends on the nature of the oath in the "world", is it 100% dependent on the Paladin's feelings, ie; could one with the most good and pure of oaths do vile and evil things, as long as they are convinced it's right, or is there any degree of externality that will come into play.
To clarify even more, if the GM tells me my powers are wavering or gone, that doesn't tell me how I feel. I might feel a million different ways about it.
You've missed my point. For the DM to apply penalties for breaking the oath, the DM must determine if the paladin did it willingly or not. To do this, the DM must determine what the paladin is thinking and feeling. Only then can they apply the punishment. That you feel that you can maintain a different set of feelings and thinkings for the character is nice, but it's not true -- you've ceded part of this to the DM, and since their word determines reality in game, whatever you're doing is pretending inside pretending.
Of course a player can hold themselves to an oath.
You, very clearly, said that a player doing so without the DM enforcing it would be something you do not like in a game.
If a Paladin's oath was to protect the innocent and they spend 6 months killing babies, does the GM need to know how the Paladin feels, or is the oath going to be in jeopardy anyways. If the Paladin is convinced that killing them is the surest way to protect them from the evils of the world, and the oath is still secure, then that is a very particular kind of world.
Let's unpack this, because I think this gets to the heart of the disagreement. What the above says to me is that the player is intentionally acting in bad faith at the table and the DM should punish their character for it. This is backwards. Either you play with people that you expect will do their best or you do not. If the latter, then the problems aren't going to be solved in game. If the former, then this isn't going to happen at all, and, if it does, it warrants a table discussion rather than the DM choosing things for the character to pay.
If a player at my table wants to play a paladin, then I, as DM, need to trust that they're going to do that. If they break that trust, it's a table issue, not a paladin one.
No, I can "feel" like I am honourable or honouring something, when I am not.
As the DM can feel you've dishonored something when you haven't. Substituting the DM's judgement for your own doesn't improve the decision making capabilities. Either you're playing in good faith with the table or you aren't. If you are, then how you think your character is doing is good enough. If you aren't, the DM doing it for you isn't going to save anything.
I can determine what my character feels, the GM determines the results. What I really don't like and was referencing earlier, was the suggestion (and I'm not sure who all made it) to ask the player what they think should happen to their PC in-game, as a result, and then doing that. What you have posted lately seems less problematic for my preferences, and really just seems to reflect your view of the nature of the paladin's oath in the fictional world. You seem to view it as solely depending on the feelings of the Paladin in question, and therefore completely mutable, only limited by the credulity of their own mind. I could have fun playing in a world like that (not my favorite but it's fine), but if I feel like I break my oath and you ask me to determine what the consequences will be in-game... that sucks.
No. I think it's important what the
player thinks the oath is. The character doesn't think. It's not real. The player is role-playing as if the paladin is real, but that means it's the player's choices animating the fiction. And, I have plenty of faith that players are more than capable of playing paladins according to their oaths in ways that are fufilling and make for a fun game. They don't need the DM riding herd on their choices to make sure that the DM's vision of the world comes true. The DM has infinite dragons for that.