incategory function
Fragment of a discussion from Project:Current issues
It's because the category is included from a template. Its a known issue (see w:help:Search)
What should we do to solve the problem? Would it be difficult to take the categories out of their templates?
From a pragmatic point of view, I don't think the benefits outweigh the cost of removing cats from templates.
This issue might go away when/if bugzilla:18861 is fixed. In the mean time you can also use tools like http://toolserver.org/~daniel/WikiSense/CategoryIntersect.php?wikilang=en&wikifam=.wiktionary.org&userlang=en to do in category searches.
