two suggestions
1. remove the user from all groups so he sees only errors... if he contacts you tell him there are tech problems
2. create some forums for sick visitors... move the guy there so he can only see those forums and nobody else can see what he posts... and he will not bother anyone... if you do it well he will not even notice
That said I would like to know how some database codes/commands to find the IP's of people... like all the username register from a certain IP... and who registered from a certain IP
Also... is there a way, or mod, for admins to see IP before members post?
Another good thing which I do not know how to do would be to change the banned message to "sorry but due to technical problems you can not post from that part of the country..."
When I ban a user... three our of 4 times they reply with insults and threats of more to come... banning a sicko no matter how you do it feed whatever it is motivates him to pester you...
You can also try to scare him but it does not usually work... but it is worth a try... say you are coming after them or that you will call the police... but tell them where they are be making a little search on their IP
If you tell him "the police in Miami Beach will come to ask you questions" is a lot more scarier for a guy in Miami Beach than just "I will call the police..."