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"...
An alternative form of spelling is @boardbitch@.
(Troll): You can't defeat The Little Red Notebook!
Member: Really (troll), can't you do better?
Mod: No, that's about par for our boardbitch