iserith
Magic Wordsmith
I am just trying to figure out at what point using OOC knowledge makes you 'a jerk.' There seems to be a line for you, I'm just not sure where it is. Why is reading the module and using that information 'jerk' behaviour, but doing the same with the Monster Manual or the setting book is not?
The point at which anything makes you a jerk is when you're purposefully taking actions that cause the group to achieve to fail the goals of play - that is, everyone having a good time and creating an exciting, memorable story together by playing.
The issue then becomes a question of why would I ever let someone's use of their skill and knowledge of a game impact my fun or the story we're telling together, either as DM or player. As a DM, only their actions matter, not how they arrived at deciding on those actions. As a player, a skilled teammate is a boon, and I'm still going to advise the player to verify their assumptions before acting on them so as to mitigate our risk.
This isn't a problem unless someone decides to make it one via the social contract.