You only get a fate point if accepting the compel causes trouble in some way; i.e. if doing the thing would be a bad idea. You don't get any points for accepting a compel where nothing bad could come from it. The rules are pretty explicit about that.
Right, but that's not a "mistake" on the players' part as it is engaging the mechanics of the game. This is the same way that the Temple of Badness can go on rotting into the Earth until some D&D party makes the "mistake" of risking their lives in pursuit of the treasure therein and earns XP for the trouble. In that way, the entire premise of OD&D is a compel on the (apparently common to all characters) aspect of "
Greedy Tomb-robbing Murdhobo."
Also, a Fate compel is not necessarily "doing the thing". You can get compelled for something happening to the character that's out of their control. For example: Since you have
War buddies everywhere, it makes sense that your old pal Colonel Mustard would show up and recognize you from the door when you're using a Fake Identity at the Duke's ball. Accepting that compel to make the scene more difficult/complicated for the character is no more a mistake for the Fate player than accepting XP for a wandering monster kill is a mistake for the D&D player.
D&D has traditionally had paladin and cleric powers be contingent upon following the ideals of the religion, because that power was only ever a gift in the first place, so of course they can take it back if you're abusing it. It doesn't make as much sense for the magnitude of the benefit to scale directly with the amount of trouble it causes you, and it stops making any sense at all for other sorts of classes.
D&D has traditionally had paladin and cleric powers be contingent upon the whimsy of the DM dependent upon sketchy interpretations of ill-defined fantasy religious strictures on either his part or the players. If your DM doesn't care (the more typical situation, IME, a than the DM stripping them away agressively), then the restrictions simply don't matter.
It makes perfect sense within the context of
Fate's design goals, which
are different from D&D's, especially WRT the original versions of the game. D&D started out as simply player (through the character-as-pawn) vs. dungeon. As a straight-up contest, there's utterly no reason to "play a flawed character", or indeed "play" a character at all any more than you "play" the queen in chess. Its a DM-mediated puzzle-game with a side order or chance and puns! The fantasy stuff is just set-dressing. This is obvious in the tone, demeanor, and structure of the older rules and particularly adventures. The basic structure of play in D&D has absolutely no interest or truck with the creation of an interesting narrative, characters, or even game experience. That is all up to the DM and players, but mostly the DM.
Its why folks even discuss "fudging" rolls or "railroading". Those behaviors only exist to preserve a storyline in the face of an uncaring ruleset. If you want an interesting or intricate story that revolves around Aragorn, then Aragorn had better not get irretrievably vaporized by a trap set up for characters with names like "Fighter IV" and "Uther Cleric" or "Melf". And when people started realizing that, they started writing new rules. (Well, first they started fudging and railroading.) Eventually that lead to things like Fate, which has the explicitly stated purpose of creating those interesting characters and narratives.
What FATE and this proposed house rule both correctly recognize is that there's no reason to play a flawed hero who makes mistakes in most games. (Which seems like an obvious truism to me, but which FATE sees as a problem with those games, which it then goes out of its way to correct as hard as it can.)
It
is a problem (perhaps a limitation would be more accurate) with those games,
when you have the goal of creating an interesting narrative and characters. This is perceptually not a problem with D&D, because it (at least in the traditional sense) is predicated on the adversarial dungeon crawl,
and many groups have figured out kludges for getting what they want despite the D&D rules. However, it becomes rather obvious in some of those other games which are (mostly loosely) patterned after D&D mechanically, but with the stated goal of having you co-create a good narrative or story.
What this proposed house rule further notes is that, due to things like Bounded Accuracy and the point-buy system for stats, it's impossible to make a character who is actually flawed in any way whatsoever in 5E. (Most games have mechanics where you are forced to have some deficiencies in order to balance against your strengths; 5E characters only have strengths, and areas where they are slightly-less-strong-but-can-still-probably-succeed-if-they-really-need-to.)
No argument, there.