personally, i think it takes away from the game when people do that. one of our players used to DM and knows all about lots of the monsters and uses that knowledge in character. if he would make a knowledge check or if we had faced that type of monster before that would be fine, but that's not what i'm referring to. he's done this many times in two different campaigns now.
also, he's been having his character act weird lately for no reason [in character]. he, as a player, just doesn't want to talk to NPCs in the campaign so he has his character get up and leave. twice, when we were in the middle of eating in the inn and NPCs approached us and he just POOF gets up and leaves the table without a word. the first time, he went to the bar and talked to the innkeeper. the second time, he went out to the stables. by the way, he plays a paladin.
that business isn't such a big deal. BUT, for me, it just ruins the flow of the scene in my head and it takes me out of the game. if there was a reason, it'd be perfectly fine thing. but for someone to be that rude, there really should be a reason and/or repercussions.
what do you all think? any suggestions as to how to handle it?