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I was thinking of this option also, if possible to add.
Instead of flagrantly just banning the user, let him think he still has access to the site and able to post, yet only admins and moderators can see the posts and by replying to that persons post, only the admins and that user see the reply.
It would circumvent the problem users and not have them try something untoward the site if they just think noone listens to them. LOL