Board Thread:Editor Board/@comment-26391060-20131101164532/@comment-6697950-20131101212811

Under "Preferences" -> "Editing", there's an option called " 	 Prompt me if I leave a blank edit summary". Apparently, if you publish an edit with a blank summary while that thing is on, the page reloads with categories forced into source. If you delete the code for the category, you'll remove the category from the page.

Of course, that was not the reason I had that thing on, but I noticed that it had another use. Though I wouldn't recommend using this method for editing sections, as there appears to be a bug with it on the section editor.