the use can create a new account by using proxy (if you are thinking that you can track the evader by the IP)
or he can use proxy with new computer , the user can refresh and delete his previous cookies to remain anonymous.
Its really hard to fix this issue if i am not wrong ?
It's little things like this that honestly worry me that this site will be taken down and I don't want it to at all.
You say "everything is possible" but not really give out a concrete way to do it. And the reality of things is: There's no way to stop people from circumventing new bans. I mean it's bad enough already that if you want to create an account anonymously with Tor you need to pay BTC because the tor node was previously banned.
The only way would be to close registrations and start an invite-only policy, but this would be against the site's interest since you would lose lots of traffic, and even then, scammers would end up finding invitations.
Let's not ruin this great forum for the legit users because of the bad user's fault.