API filerepo (such as the one provided by $wgUseInstantCommons) doesn't follow redirected files at the shared repo.
This is a problem for reusers, whose file can "disappear" even if commons admins were careful enough to leave a redirect behind.
Version: 1.21.x
Severity: major
URL: http://translatewiki.net/w/i.php?title=File:File_redirect_example.jpg