EzekielRaiden
Follower of the Way
But by definition, simply by having any backstory at all, the player does this. Immersion damaged from the outset.The PC/player distinction I brought up earlier. If the player is clearly different than the PC because the player is exercising control over the fiction in a way the PC couldn't, then it feels less immersive.
Note this is not a "perfect sim is impossible therefore don't even try". It is that the standard you have set here is that the PCs cannot, ever, for any reason, have any control over any content in the fiction, unless by the one method of the character personally acting upon the world. This is incompatible with writing a backstory for the character--flatly, absolutely. There cannot ever be a case where the GM would ask the player about something from the character's backstory. Either the backstory must be purely randomly generated, or it must be pre-generated by the GM and handed to the player.
The vast majority of sim players (and I suspect that probably includes you!) don't play that way. They do allow control over aspects of the fiction that the character should know and other characters might not, even if such knowledge does affect the world and can make a big difference in the long term.