He can't be a bot. He's been here since 1996 or 1997, which is probably too early for a sophisticated AI that is able to attempt to respond (however feebly) to insults.
He also might seem to be mentally retarded, but I remember the mods once saying he was using multiple VPNs or something to escape moderation, which would imply a level of intellectual ability.
I think he might be a professional troll, possibly associated with a large organisation like FLG or some government agency, and his mission might be low-intensity disruption/crapflooding.