Board Thread:Support Requests - Community Management/@comment-1990160-20130617141044/@comment-452-20130621032433

I'm not going to go through all of the examples on the page you linked in your first post, but here's one at random: I would assume they are trying to add helpful categories but don't understand your category system. (Unless you have had a past problem with that particular user ignoring previous communication not to do so, in which case you have a user-related problem, not a category-related problem) The categories added in that edit are existing categories, so my method of watching all categories would work here.
 * http://leagueoflegends.wikia.com/wiki/Category:Ranged_champion?diff=prev&oldid=1820827

I see that you have 532 categories, but I don't see why that is relevant.

If you wish to be informed when a page is added to an existing category, follow my suggestion, if not, don't.

My watchlist consists of 14719 pages, 237 are categories, some of them non-existing categories which are commonly added by well-meaning people who don't understand the category system.

I didn't notice that this thread was in "Community Management", I usually answer technical questions, so I gave a technical solution, so I'm sorry that that wasn't what you were after.

From a community management perspective, here's some obvious suggestions:
 * Making a "category guide" help page.
 * Posting a news post about how your category system works.
 * Linking to the category guide from the welcome message, community corner, or whatever you use as a hub for new users to familiarise themselves with the wiki.
 * Linking to the category guide from MediaWiki:categoriespagetext or MediaWiki:Categories-summary, or writing a short summary regarding category usage.
 * Ensuring that all 532 categories have individual descriptions stating the purpose of that particular category, and what pages are intended to be placed in that category. (A well-oiled category system should do this, regardless of how many categories there may be.)
 * Instead of using rollback, writing a message in the edit summary regarding why the category is being removed.
 * Contacting users directly about adding invalid categories, with helpful advice about how categories should be used. (You said earlier in the thread that they rarely do it more than once, but I'm listing this here anyway for completeness and for the benefit of others looking for suggestions)

I hope this helps, good luck!