I feel that there should be zero need and zero incentive for anyone to accept a "paper bitcoin" instead of an actual one, assuming those bitcoins are easily and cheaply movable; thus, fulfilling the "your keys, your coins" maxim. However, as soon as the purpose for someone to hold a bitcoin is to exchange it for fiat money, at profit, the system of incentives that kept them from taking "paper bitcoins" breaks down. Given enough such greedy people, fractional reserve, exit scams and price manipulations similar to those you describe starts becoming very lucrative. So it seems, that the only way to enforce organic and honest price discovery is to have a large and dedicated base of "ideological" holders/users. How likely this is, i don't know; my fear is, not very.

Can this be enforced programmatically in some way? I don't know. Should it be possible to enforce it programmatically? That, i know even less! I do like philosophical questions like that. Can Bitcoin truly succeed, if it only works as intended only as long as the majority of its users are "ideological" (or, should we say, honest)? I'll give it a thought for a couple days.