[Max Taxable]

Originally Posted by Simon Lloyd

My advice? let him join, welcome him as a user then add the mod "miserable user" and add him to it, he'll always be able to see and use the forum except it will be painfully slow, if he re-registers simply add his userid/username to miserable user eventually he will get fed up.

Again, that one only works when he is logged in. One could also add the IP address as well to MU, but as the OP said he changes them often.

If you make the settings subtle on that however it might be some time before he begins to suspect there's a problem.