(1) This thread is in general RPG. Not D&D. There's a reason for that.
(2) I'm not saying that players should or shouldn't do anything in every system. The OP invites discussion about various ways in which true descriptions of PC actions might be established. The current discussion has moved on a bit from that, to also talk about how true descriptions of PC choices, PC emotional states, etc might be established.
(3) If someone's answer to the questions posed in the OP is the way D&D does it, end of story then they're welcome not to participat in the thread. If they're going to make ungrounded assertions that nothing else is really possible, well that's not very helpful either and is fair game for clarification or correction.
(4) The most interesting thing for me at the moment - obviously I can't speak for others - is what are the necessary conditions for a genuine challenge to character concept? This is what @Ovinomancer and I have disagreed about - I believe without undue acrimony! I would be very interested to hear what @Campbell, @chaochou and/or @Aldarc thinks about it, should they care to weigh in. (Of course it's their prerogatibe not to.) My own views on this are heavily influenced by a certain conception of GM role in terms of framing scenes that put players under pressure by putting things that matter to the PC at stake. I don't know Exalted at all except from Campbell's accounts in this and other threads; and my experience with PbtA games is fairly limited, although I know the rulesets for DW and AW fairly well.
Yes...
But I'm not making ungrounded assertions. I specifically said that Burning Wheel is fun, but not the average experience. This is not ungrounded, it is, in fact, grounded by any statistical study on RPGs you can find.
My point was not that you are a wrongfunnotmywaydonogooder, but that D&D is (though not necessarily should be) the baseline assumption. If we can't argue from a base of some sort, then there is no argument.