Banning is an admininstrative decision. If someone repeatedly acts in a manner contrary to the forum rules, they will be banned. The ban is for the user, not the username. That is why multiple usernames are not allowed.
If the offending party came back under a different name, and acted civilized, we would probably not notice right away. But to use a similar name and post in the same offensive manner will result in another ban.
Any questions? Contact any of the moderators, or hit the SPAM! button and ask away.
Cheers.