As noted at:
The full edit page form is shown when you get to the edit page for a nonexistent page when page create permissions are disabled, as on English Wikipedia. We should be getting a View Source box or similar error instead.
Further, when submitting the page to be saved, it just pops back to the 'this page does not exist' instead of displaying an error message.
This is likely a regression caused by the recent changes to permissions error reporting.
Version: 1.11.x
Severity: enhancement
URL: http://en.wikipedia.org/w/index.php?title=SDLFkjkfsd&action=edit