I’m not sure of this. It seems at least possible that we could get an equilibrium where everyone does use the unfiltered UP (in some part of their reasoning process), trusting that no one will manipulate them because (a) manipulative behavior is costly and (b) no one has any reason to expect anyone else will reason differently from them, so if you choose to manipulate someone else you’re effectively choosing that someone else will manipulate you.
Fair point! I agree.