Board Thread:The Panopticon/@comment-20607870-20160103215509/@comment-5918438-20160104153552

I would recommend at this point that you start trying out source editing. If you click on the little arrow next to edit, a dropdown will give you that option. There, in the bottom left corner, is a list of all the categories on the page. You can remove this category from each page there by hitting the trash button next to the name.

Otherwise, in VisualEditor (the editor I'm assuming you typically use), you remove categories the same way you add 'em. Options > Categories > Click on category > Hit trash