SomethingAwful does the mod-dictatorship thing pretty well. It's a two-step process to get banned (you're probated first), it's a three-step process to apply a ban (roughly: user reports, moderator applies for a ban, admin approves), comments are clearly marked as being responsible for bans, and there's a complete, public log of probates and bans complete with justification and which mod/admins were responsible for requesting and then approving the probate or ban. The watched watch the watchmen, so to speak.