I noticed on ms.wikipedia.org when switching to vector I got a red link on "feedback page" although I was sure they had one.
Turns out appending &uselang=ms fixed it.
Compare:
http://ms.wikipedia.org/w/index.php?title=Khas:UsabilityInitiativePrefSwitch&uselang=ms
http://ms.wikipedia.org/w/index.php?title=Khas:UsabilityInitiativePrefSwitch&uselang=en
Version: unspecified
Severity: enhancement