I guess I just disagree that metagaming is the problem there. Again, the problem is "adversarial mindset", the vector is metagaming. You can ban metagaming but that does nothing to disabuse the adversarial mindset. Also, just, my life experience has been mostly that metagaming just happens and isn't done to be adversarial. Its generally easy to pick up on the intentions of my players, and even when they metagame it's mostly been by accident? Or more, obtaining the OOC knowledge was by accident? "Oh is this Horror on the Hill? I remember Horror on the Hill." "Oh... I just saw your notes about Lady Kerila " Just, oops! They know things! They aren't doing it to 'get one over' on me, or 'win at any cost'. And, well, I don't want my players to turn off their brain during the game, an if that factors into their decisions, so be it. Describe the action and we play the scene, its fine. This is over 20 years of dozens of gamers, btw. And I know that people in this thread already disagree with this stance, but yeah I'm of the mind that trying really hard to pretend you don't know something you 'shouldn't' to make your actions is functionally equivalent to making actions based on knowing something you 'shouldn't' in terms of metagaming.*Exactly.
To me it’s indicative of an adversarial mindset on the part of the player. A need to win at any cost. You’re playing an RPG, so roleplay your character. We’re playing a game with dice, so accept that you won’t always succeed. We’re playing a game that centers combat and death, so accept that sometimes it will come around to you. If you need so badly to win that you read the module beforehand? Come on. The recent versions of the game aren’t so wildly lopsided in your favor as a player enough already as it is that you need to metagame, too? Come on. You’re all but guaranteed to win anyway, graciously take a lump or two on your way there.
Again, for a lot of people, metagaming is harshing the vibes and being a jerk.
As I said, I'm too tired to care. If more time is wasted trying to find either an in-character reason to have some piece of knowledge or to figure how to act around the forbidden knowledge, than actually just playing the game and moving on, I just tell them to metagame. It's fine. Ok, you know that Kerila is a vampire, what do you do now? Ok, you know that you aren't good enough to sneak past these guys, what do you do now?
*To actually pull a from-a-table-real-example of this, Episode 15 of the Critical Bits podcast has this happen. One of the players knows that the NPC they're talking to is an evil clone, but they 'don't want to metagame'. So they spend around 10 (edited) minutes floundering around trying to act in a 'proper' roleplaying way, that their character doesn't know its an evil clone. So even though they are trying to act 'in character', in good faith, they are still making character decisions based on knowing something they 'shouldn't'. As a podcast this was very funny, because the player and DM are professional comedians, but as a DM in my home game I would've just let them have it and played out the scene from there. This is mostly a philosophical difference that I don't really intend to resolve, merely explain.