I thought about that. Something like X community notes feature but where Nostr folks who are not connected and who normally disagree, and here they agree - it can apply a filter label. And people can opt out of various content. NSFW, Explicit, Violent, Religious, Political, Investment, etc. But it would have to work like community notes concept or a few can sandbag someone into a commonly filtered category.
Discussion
Check out NIP 32 labels. In coracle, you can "tag" any note with any arbitrary string. It would be possible to add a longer form description to those tags.