Sounds like a right jerk. But I don't know if keeping on suspending the accounts would deter him any. None of them contain anything he cares about, they're just a means to an end and he'll keep on creating them. I wouldn't be surprised if they did things like ban his email addresses from creating new accounts and he went and created new email addresses, too. Banning IPs doesn't really work either. That just leaves restricting commenting and PMs to people you give access to, unfortunately.