Possible Enhancement Suggestion here.

Add a list of nicknames that users aren't allowed to switch too, and a permission to override that list.
Obviously strip color codes when comparing to the blacklisted nickname.

A lot of servers don't really mind that Users change their nicknames freely, but them changing it to a Staff's name or notch/jeb_ can be a little annoying.

Just a thought. Delete if not interested. :)

Great suggestion, would love for this to be implemented with!

Agreed

Realistically there's no need for this, just thought about it, there's plenty of plugins out their that can block things from being said in commands/chat, check out PwnFilter or Chatcontrol.

This has now been implemented - you can download the latest version from here.