I had that kind of player on my parties. They run in perma-silence, if you are playing on PS3, make a macro or something "Imma playin' on PS3, won't talk too much! thanks!". Also, we put a lot of effort on finishing the run and they leave just like that. Ungrateful b***rds. Thankfully, I didn't have a full party of them, just 1 or 2 guys like that. I can't even blame the game for this, since it didn't give me a reason to play as a quiet/ungrateful player.