Normally if you visit the talk page for a non-existent user, such as https://www.mediawiki.org/wiki/User_talk:NoSuchUserBAD, Article->showMissingArticle() displays the error message 'userpage-userdoesnotexist-view':

User account "NoSuchUserBAD" is not registered.

But if Flow occupies the User_talk namespace, you get no indication that there's no user account corresponding to the page, e.g. http://ee-flow.wmflabs.org/wiki/User_talk:NoSuchUserBAD . You can edit the Flow board header and create posts for a non-existent user's talk page.

Version: master
Severity: normal