I think the solution is to give users an option to put a paywall for new communications, i.e. comments by strangers in your threads and private messages from strangers. That is sufficient to discourage any kind of spam or unwanted information. If I follow someone or write them first, that means I agree to receive dickpic from them. What's the deal? Just unsubscribe and it's done. No need to introduce centralised censorship, just introduce optional payment to write in my threads or my DMs. I want 100 satoshis from anyone new writing to me in DM or writing comments under my posts. Just give me 100 satoshis and I agree to receive spam or porn and immediately block such users, collecting 100 sats from them.