Expressing the hierarchy
Someone asked me to explain my changes (as they should!).
It's a pretty small and subtle change. John (I presume) described the categories as forming a (shallow) hierarchy -- with a set of "Master" categories that are (supposed to) partition the set of pages (i.e. each page should be in one of them), and some other categories that are sub-categories of particular master categories (like Fan, Pro & Mundane are of Person). But he didn't actually express this hierarchy -- he put all those categories in Category:Admin. All I did was apply that; making a Category:Master Categories entry, putting the listed master categories into it, and putting the listed sub categories into their appropriate parent.
This has a few (subtle) effects. One is that Category:Admin is a bit easier to read (IMO), since it doesn't mix up so many different kinds of things. A second is that it's easier (for experienced MediaWiki people, at least) to understand the category structure, since it's described more using the tools provided by MediaWiki (categories being in other categories, rather than flat). A third is that the Categories (like Category:Publication) that have sub-categories will have automatically updated links to them listed under "Sub-Categories".
The other small change I made was to put the *descriptions* of the master categories onto the Category:Master Categories page, and transclude (automatically copy) them from there onto the Categories page, rather than having two separate (and maybe out of sync) copies.