@AltCode One significant potential issues with listing all followed categories in the same kind of layout as /categories is the below-the-fold effect, or the page-2 effect as one might have called it in earlier times. Whatever categories end up falling below a certain scroll distance will just never been seen by most users. If you follow a lot of categories, the ones that end up closer to the bottom of the list than the top will just end up ignored. It doesn't encourage participation, and it also doesn't discourage following a lot of categories that you don't actually care about.
And follow relationships are very important under ActivityPub, since they dictate content flow. Bringing in a lot of remote content that no one on the local forum is actually reading or engaging with is very wasteful.
An easily accessible compact list might be better, with different sorting options so that users can choose to have categories with new content float to the top. Usually with forum categories, you want the ordering to be static, but that expectation won't necessarily be there for just a list.
