I feared that, indeed. I genuinely need a plugin that acts the way subreddits do. Maybe that’s too difficult? BuddyPress has groups; anyone can create their own group on a niche and anyone can join however many groups. Each group has their own activity stream where the group’s members post niche-relevant content. But they’re also customizable, with group bg and pfp.
@Mittineague Tags are okay, it doesn’t offer any ways of customization and a sense of belonging as groups do. They’re not bad either, however.