Circling back to what seeker4 said above about categories here being an ill-thought out mishmash of genres and formats, it would be far better if our "format" type categories were entirely separate. So:
Microfiction
Flash Erotica
Novel
Poetry
Story
Were entirely removed from the other categories and were separately filterable. That way, we would retain the main category so you could have a Flash Love story, Flash Masturbation story, Micro Spanking story and so on.
But TechGoddess, among others, have already said this isn't desirable in Novels because each chapter is not necessarily "about" one thing. That's a by-product of some authors making each publishable piece multiple chapters, but that's down to author preference.
My argument, for engagement and readership, should be that any chapters containing multiple different scenes should be broken into smaller chunks and linked individually and "tagged" (categorised) to help readers find what they want. That's what drove this entire discussion. That way, people can dive in if they find a scene that matches a category they like, and if they enjoy your scene, could jump back to the start and take in the rest of the novel that they might never have found otherwise, or thought: "Novel? Ain't nobody got time for that!"
Rejigging and splitting chapters is a lot of work for those authors who have invested time in writing novel-length content so it's unlikely to happen.
Overall, it would probably be helpful to subgenre the rest. 'Fetish' is a bit broad and imo would be better if it were axed, leaving the other fetishy things to take over. We could use Fetish as an umbrella term, but who's to say whether Cross-dressing or Watersports or Facesitting is or isn't a fetish? And BDSM? The masks, whips, chains and cages end of the spectrum is arguably fetishy to some, but completely normal to others. Tying someone's wrists, blindfolding them and teasing them with a feather is BDSMish, but it'd hardly be classed a "fetish" in most people's definition. It doesn't seem fair to marginalise one and not the other, so if I was redesigning the structure from scratch, I'd let each topic stand alone and be specific to an act rather than a type.
But then it gets murkier still. College Sex? Teen? Hardly acts. Those two are pretty much the same, barring mature students. Then there's MILF and Mature, again, types of people not acts. So maybe splitting categories further into broad sections would have been better: "Act" and "Characters" for example. Then we could have Teen + Anal + Flash. Or MILF + Exhibitionism + Novel.
But then we have 'setting' too. Fantasy. Sci-fi. Supernatural. Historical. Medical. Money. True. Etc.
So that begs the question: should there be a 4th umbrella group...? It's neverending.
At that point, it starts to make stuff really hard to find, if people need to know that they're looking for an act vs looking for a setting or style of story. So does it simply make sense, as seeker4 says (and I'd love to have), to scrap categorisation altogether and just use tags as the default search feature?
But then the concept of the Omnium badge disappears, and that's quite a draw for people who like stretching themselves. Soooo.... I dunno.
I doubt anything's gonna change soon anyway. But it's fun to think about ways to make this place better for both authors and readers to connect more easily and find content they want to consume.