@roz Most posts have been clear on that front, so I must have missed any broad assertions that there's a 'one true way' from a wide array of posters.
That said, I do think people do this anyway, all the time, as a normal part of gaming. While people talk about how annoying it is that somebody didn't read the books/watch the show/read the theme files for the game they're playing on, most have or do.
Almost universally, these documents or source material include a wide array of very important things that the players know, and the characters (or any specific character) do not or cannot.
The majority of players are already accustomed to this. It's already baked-in. If someone says or does something they wouldn't know as their character IC, wrists get slapped for it; that's also already baked in. We have all survived this or we wouldn't still be here doing this at all.
As a result, ultimately, this is not a question of people being able or unable to do this, or us not having means of dealing with it if the issue arises. It's a question of how fine-grained we want to get regarding transparency or secrecy.
It will work differently for different games and different players. This isn't really a matter of it being exhausting to suss out, though.
"Dude, your char wouldn't know that, that's not public info." "D'oh, my bad!" is not a world-ending crisis.
Neither is, "Hey, how would your character know that?" "<reasons>/Oh, shit, you're right, I wouldn't, sorry! Reposing now!" "OK, cool!"
Both of the above are pretty common in healthy game communities, regardless of their stance on this. Fostering a healthy game community in which the above exchanges are the beginning and the end of it, without snarling accusations of cheating at people who simply brain-farted, or people being terrified to provide any RP hooks that hinge on secret information IC, is far more important than any call someone could or ever will make on how fine-grained they go on providing information in the first place.