I feel like a better NSFW system would have three tags: sexual content, graphic violence, and NSFW/other. And then you could choose a severity for that tag, like "mild" vs. "severe". Then if the content gets any of those tags, it's automatically tagged as NSFW without user intervention.

That would allow for example the OP to avoid porn (severe sexual content), but still see the memes (mild NSFW/other) just fine.

I'm not a big fan of the acronyms, as they often obfuscate the underlying meaning. Sometimes plain words are better.

If you see a porn community, you could just block that community and you won't see stuff from it anymore.