This is a good topic. My internet persona is very similar to IRL personality I think. My physique resembles that of a second-hand rake and I've had a fair few problems in life and I think that really does reflect over the internet. For example, I was brought up with the whole 'only do to others what you wouldn't mind them doing to you' concept.
I dunno if many of you know, but I don't think I've ever outright insulted someone straight to their face on toribash (whether it be forum, irc or ingame) and I'm generally a bit of a pacifist when sorting out bans and stuff. I think this is the same because of how I am both physically and mentally irl. I'm a pretty huge coward IRL because if I do go around saying shit I'll probably get broken, this means that over the net I am not comfortable insulting people and it makes me feel bad. Oh no that was long.