A "boardbitch" is a harmless, and somewhat tolerated, troll on a message board, whose attempts and responses to flaming are weak, if not outright lame.
The sign of a good boardbitch is one who takes repeated abuse and keeps coming back for more. Often, the forum will keep the boardbitch around as their "pet"...
A "boardbitch" is a derogatory name given to a troll on a message board. Instead of outright banning the troll, the mods will keep the troll around to be the message board's "bitch".