So, on an impulse I tried to test out the name filter function today. I added 'Bobby' to my name blacklist in the database, then logged in and tried to create Bobby the Berzerker Gnome.
Instead os give the "This name has been rejected" message, it give a "Names can only contain numbers" error.
Granted this prevents people from being able to use that name, I just wanted to make you aware of it, if you weren't already.

lol, can only contain numbers?

lol... okay "it cannot contain numbers"

Perhaps LE can allow us to customize the response, such as
"Name rejected because it sucks. Either create something original for once in your life, or go back to playing WoW."

L337 ]<0mM@nd0 FTW!!

Heh unfortunately not. The error messages are hard coded into the client, we only send the error number to the client. We apparently are using the wrong one for the 'name already in use'.