Pay the evil fee to an escrow, and if they are not banned in their first 30 days/after their first 100 posts/whatever, the payment is returned. Bonus points for doing so over Lightning to keep fees low.
There's 2 problems with this:
1. It makes me look very shady.
2. I can't verify the evil fee they have to pay.
The problem is that unless it is someone I knew from outside the forum (and no one I know outside the forum knows my forum handle), then it is near impossible to differentiate between a user who has previously been banned and someone who has just been unlucky with their IP address/is using Tor.
True. I don't want to announce my criteria in public (nor do I have strict criteria yet), so I'll leave it up to the user to convince me.
Perhaps if the person could prove ownership of a Reddit account, Twitter account, or similar, which is in good standing and has displayed good technical knowledge, but such users would be incredibly rare and even then it isn't a guarantee.
All good suggestions
But I don't want to limit it to users with good technical knowledge.
I'll see how this turns out. So far, I had one request, which I rejected.