Abe Sokolov
Abe Sokolov (sometimes known as "Dr. Abe Sokolov") is a pseudonym of a well-known internet troll on wikipedia who goes by the username 172.
English Wikipedia User Richardchilton calls him "the only admin who tries to help protect left wing users from persecution".
Abe Sokolov is claimed to be largely responsible for the break-up of the Wikipedia red faction, although some users such as English Wikipedia User Lir have indicated that the faction still exists, but has moved underground.
Abe Sokolov's Userpage (User:172) on wikipedia
Abe Sokolov on factionalism and sysop vigilantiism
Abe Sokolov's troll-friendly defense of English Wikipedia User RK -- see also Dueling POV.