User blog comment:Shadow125787/Opinions, Categories, and so forth/@comment-4536066-20111028152044/@comment-4520133-20111030211818

Enter the page's editing mode, then on the side there's a list of the categories it is linked to; there is the place where you delete them.

Also the "Incomplete Articles" category is there so people can quickly link to pages that need finishing. Again they can always be removed from that category once finished.