Or just…say “fuck that” and avoid this entirely pointless addition to the social mediasphere. Simple as.

Bullshit. Threads' algorithm will severely deprioritize external posts. It already heavily favors sponsored instagram accounts as is. You're not being smart by putting porn on Threads through a Mastodon instance. Their AI will take whatever you have that's tame and refuse to show what's dirty. And if you do too much dirty, well, being shadowbanned on Instagram is a fucking super common story as is.

All this idea achieves is doing content charity for Facebook of all things. Defederate. It's the only correct move.

If you federate with Threads, dont Meta have that federated user and content data cached on their servers? Producing content outside of Threads and posting it to Threads still gives them content, and information about you. Much like how people without Facebook accounts still have shadow profiles from being featured in Facebook users' pictures and posts. The only solution seems to be (though maybe I misunderstand) not to federate or engage with Threads servers. This would be too philosophical a point for the vast majority of Internet, and especially ex-Twitter, users. Mastodon instances would have to explicitly defederate which could kill their userbase if the traffic flows to Threads, which it did in a matter of hours.