When going to the protect action on any 1.18wmf1-wiki, MediaWiki fails to find the message for the special 'sysop' case.
This results in the interface being rendered with 'protect-fallback' instead which, as it should, assumes that the passed variable is a user right. However, sysop (which is internally mapped to 'protect' && 'editprotected'), is a user group and should have (and does have) a special dedicated interface message.
This works correctly for me in the development trunk, but on nl.wikipedia.org and mediawiki.org this is currently failing. Perhaps something wrong with the localization ? Or a bug that was fixed but not backported from 1.19 to 1.18 ?