Wikimedia Bugzilla is closed!

Now they are written in the user's chosen interface language. Since the
summaries are for others to see, they should be in the project's language.

The summary is set on Article.php, function rollback():
 $newcomment = wfMsg( 'revertpage', $target->getUserText(), $from );

I think the function that should be used instead is wfMsgForContent().

Thanks.