Original bug title:
<translate> transferred to translation subpage when entering a translation at [[Special:Translate]] that contains a non-closed <nowiki>
This should never happen, I guess:
http://commons.wikimedia.org/w/index.php?title=Template%3AWatchlistNotice%2FTranslation%2Fde&diff=96853588&oldid=96853388
Result: Translated page (the /de sub-page) was listed at [[Special:PageTranslation]]
Outcome
Old bug report was tested and it was found the issue no longer exists.