Putting the Unicode issue aside, we all know that name-banning is not a _solution_; it's just a _tool_. `:)` "Banning" is the wrong word to use entirely, so it won't appear anywhere in the interface. 'Preventing names from being re-used' is useful for managing spam-bots and unsavoury names.
A full IP-based banning system might appear far in the future, but ultimately it's up to the forum-admin to be able to manage their site and community.