Problem: For several years now, categorization changes have had dedicated entries in recent changes and watchlist. This is useful for watchlist – when you watch a category and have categorization changes enabled, you can see recent additions and removals to the category. For recent changes, this isn't that useful as it lists changes to any category.On Special:RecentChangesLinked ("related changes"), it only shows additions to the category (and also categorization changes for other categories).It happens because when you remove a page from the category, it is no longer "linked" and thus it cannot be listed in the related changes anymore. Consequently, there is no native way to see all category additions and/or removals, and only them, from a single place.Additionally, there has been some technical debt around displaying the categorization changes. For example, sometimes it's unnecessarily difficult to access the diff.
Proposed solution: (one of these)
Improve Special:RecentChangesLinked to implicitly show additions and removals of the category (when you have categorization changes enabled)
Create a new special page dedicated to category changes (similarly, there is Special:NewPages for pages creations)
Who would benefit: Wiki gnomes checking for mistakes, patrollers checking for vandalism, wikis with complex categorizations
More comments: None of the above should require any major changes to the storage, it's just a matter of displaying better what is already being saved. Since this all is backed by the recent changes, the changes are only traceable for the last 30 days. There is also a proposal (phab:T6366) that a complete history of all category members (and time of their addition/removal) is stored, but that would probably be an epic task.
