Steps to replicate the issue (include links if applicable):

• Go to Special:CreateAccount as anon
• Type in a existing temp user account like *Unregistered 1

What happens?:
The message "Username entered already in use" (userexists) is shown

What should have happened instead?:
I expect the message "You have not specified a valid username." (noname) which is shown when using a not existing temp user name like *Unregistered 1234
As every name similiar to temp users are invalid, it is not useful to say something exists in that pattern.

Software version (skip for WMF-hosted wikis like Wikipedia): master