I believe the term "Ironic Persona" sums up the spirit of trolling best. The best trolls, like Skin and others, are the alter-egos of some normal, nominally sane person. They do it for the sake of driving other people nuts or for reaction. Examples: Jillian, Skin, Wordin, Jack, Me.
This distinguishes what I'd call "crusaders", people who troll because they have a specific beef with a board or admin. Examples: Che, Miss Manners, Cait, CU.
Then there are people who just like this board, not fish or foul, but who like socializing here. Examples: Aurian, BDM, Dark Link, TQ, Eggs, Gagh, LG. Some of these can be troll-like, but I think they are here for the cookies.