I’m not very familiar with the ActivityPub protocol, but there are easy ways to flatten an hierarchy.

For example, the tag could literally be “NSFW/Porn/Straight” - though I assume then there’s no system in place to request tags by their parents… So posts with that tag would just get 3 tags: “NSFW”, “NSFW/Porn” and “NSFW/Porn/Straight” in the API, and would be hidden / breadcrumbed in the UI.

Though it’s not ideal to do it like that, as it would make maintaining structure more complicated - though not impossible.

Just curious, how open / extendable is ActivityPub? Just to say “the protocol doesn’t have it (yet)” - doesn’t mean it can’t be implemented, either properly or through some workaround like mentioned above