is
the game IMO. How a mafia game pans out depends greatly on the metagame - tactics employed in previous games are reused, modified, bluffed with and referred to all the time in current games, and as a tactic or gambit becomes popular, the game will shift to put greater importance on it.People's changing play-styles go hand in hand with this. Being a good Mafia player isn't just about winning in the context of the game you're in, it's also being able to win despite how the last 10 games went for you. Night one kills and the subsequent discussion tie into this as well, since the established "good players" make good targets for the mafia.
So yeah, I think info from outside the game is definitely OK (obviously as long as you're not breaking the rules about talking about the games you're in). If you know how someone plays and how they react to certain situations, you should definitely use that knowledge. And, conversely, expect it to be used against you.