[dethfire]

Originally Posted by Logician

If you use "usernames", it will not very efficient as banned user might have a different username, or worse, a different user might occupy that username in the other board. I think the system might be more efficient if you used email address of the banned user but I'm not sure if it would be against privacy to distribute the email address your board publicly to other sites.

I think you already thought of hosting a private forum where only other site admins have access and you share your banned email address there?

right, because my forum is part of a science network, but I understand your points