[SoftTalker]

I know exactly what you're talking about with community-killers. They don't really violate any explicit rules but they poison every thread with endless argumentation and always having to have the last word. I'm on a forum where such people are given two-week bans to start, and eventually perma-bans if they persist. It works pretty well but they will often return with a new account and start over.

Moderation is endless work if your community is attracting new users to any degree.