This page is intended as a practice guideline for wiki moderators.
There is enough content on the Wesnoth wiki to make systematically editing it quite difficulty. ESR did a sweep of the entire All Pages list during the run-up to 1.4 and found a very large amount of cruft -- over 70 out of approximately 400 pages that were junk or obsolete, and a lot of links that had not followed page revisions as they should. A large part of the reason these pages fell through the cracks is poor site organization.
To address this, ESR greatly extended the category system. Almost all pages now have a category, with most categories having fewer than 40 members. This has at least two effects: (1) Individual categories won't be too large to be systematically edited by one person, and (2) junk pages will be fairly easy to spot, because they'll either be categorized and stand out because they don't belong or show up in a relatively small uncategorized list that can be checked frequently.
In the future, we'll want to extend the categories system to preserve these properties. As an example, currently the Factions category also includes eras and races; when it gets too large, splitting one or both of those out will probably keep the chunk size of the individual categories low enough to be manageable. As another example, Translations is a catch-all for both translation status pages and translations of English-language master pages; it might be a good one to split further down the road.
One thing you should be careful not to do is to give translated pages categories other than Translations. If you do this, they'll introduce a lot of noise into category lists of master pages, and some categories will become difficult to edit again.
The current categories list is here. The list of uncategorized pages is here. If you are a wiki moderator, one of the things you should do occasionally is look in that uncategorized bin and consider what should be thrown out, what should be moved to an existing category, and what (if anything) requires a new category.