There's a perennial problem over what to do with "eponymous categories" - whether (for example) "Category:London" should be assigned as a "subcategory" of "Category:English cities", and if it is, whether "London" should then be taken out of the latter category (see http://en.wikipedia.org/wiki/Wikipedia_talk:Categorization/Eponymous_RFC for a discussion that shows there's currently no entirely satisfactory solution). Anyway, the problem would largely go away if the following feature could be implemented, and I wonder if it would be feasible.
The idea is that we could "map" a page to a distinguished category (for example, the syntax [[Category:Xxx| ]] with a space sortkey would cause that category to be the distinguished category for the current page, say [[Xxx]]). This would have two effects (besides placing the page in the category as now):
- on the [[Category:Xxx]] page, an additional category box would appear containing the "Categories for Xxx", i.e. the categories to which [[Xxx]] has been assigned, even though Category:Xxx itself has not been assigned to them;
- on any other category containing [[Xxx]], there would be a category expand button (a + sign or something) next to Xxx on the list of pages, which would expand to the category tree for Category:Xxx (thus allowing access to Category:Xxx from every category containing Xxx without the need to make it a "subcategory" of all those categories).
I know it sounds complicated, but I can assure you it would make this functionality much slicker for both editors and viewers.