Thread:Ranmyakunotenshi/@comment-4011511-20121111221925/@comment-409884-20121111222622

As to adding duplicated categories - There is a bug in Wikia where if you edit a page and save it if you click on the BACK button of your browser and make other changes then the wiki will Duplicate the categories that are already there that were manually added.

The categories that are added via a template do not get duplicated.