Board Thread:Support Requests - Getting Started/@comment-961279-20141213195046/@comment-452-20141214131435

Have you tried asking Staff to disable it?

The Customization Policy recommends against obscuring interface messages. And the Terms of Use forbids intentionally obstructing the proper functioning of the user interface.

For instance, I know that some wikis have an "add of all the categories" style of categorisation, which leads to an unorganised mess. Many wikis have Category:Characters - some wikis allow articles to be listed in that category, more organised wikis have character subcategories which contain articles. These users may simple not understand that you use a more organised system.
 * If users are adding nonsense categories, than that warrants a block.
 * If users are adding categories in good faith, but do not understand your category system, then you need to educate the users about the category system - perhaps a blog post, or a sticky forum post.

Personally, I addressed the problem with CSS: .CategorySelect.editMode > .toolbar:before { display: block; content: "This is not a search box. Do not add nonexisting categories."; float: left; color: red; line-height: 1.7em; } After adding that, the number of anons adding nonsense categories has decreased, so a similar warning might also work for you.