I’m sure the audience will find it anyway without spamming the entire Fediverse with your porn preferences. Announce it on your nsfw instance and it will be sufficient.
Edit; oh boy, the gooners sure are taking this personally. Chill nobody is taking your porn away but also nobody cares about your little porn kingdom.
Edit 2; it seems that there has been a cleanup and the admin at that porn instance is working on it too.
Final edit: Now I know what hell it must be like to be a teacher with an unruly crowd of horny teenagers that can’t think beyond their genitals. Oh, well.
Would it make sense to ban NSFW communities here, and let them start a separate announcement community for those?
Yes. One on the particular instance should be sufficient. People looking for porn will know to check out the announcements on that instance.
I want to disagree with you, but it would work just fine as you’ve laid it out.