I wonder if I may make a suggestion. We seem to have a plethora of trolls at the moment and lots of posts which are being closed with the message "Clone of a banned user".
Is it possible for anyone new who signs up to the site to have to wait perhaps 24 to 48 hours before they can actually post anything? Once they register, but before they submit their first post, their online ID could be checked by a moderator/admin (sorry, I'm not clear who does this) and then if it's a clone of a banned user, then they could be barred without ever having managed to post and waste our time. If they're found not to be a troll, they would receive an email confirming that their registration has been accepted and they can now post.
Whilst I realise that it might be a little annoying for genuine new users who would like to post immediately and get a quick answer, I would like to think that if they genuinely wish to use the site in the long-term for its intended purpose, then they would probably be prepared to wait.
Apologies if this has been suggested and considered before but isn't possible.