Last modified: 2014-08-22 11:46:44 UTC
I've created a page that shows the problem: https://en.wikipedia.org/wiki/User:MarkAHershberger/preBug and https://en.wikipedia.org/wiki/User:MarkAHershberger/preBug2 It looks like tidy sees the error (<pre> isn't closed) and fixes it, but the wikitext parser doesn't know that tidy has done this and treats the [[Category:...]] as if it is inside an area where wikitext is not interpreted.