Translations:Extension:TitleBlacklist/25/en

The username for new accounts will be regarded by Titleblacklist differently to the way it regards new articles. Titleblacklist will prepend "User:" (or its localized equivalent) to the string that a user enters at  on the create account page. So when Titleblacklist is performing matches with your Regex's, as found on MediaWiki:Titleblacklist or MediaWiki:Titlewhitelist, it will match against "User:" +.