I got a number of answers that sound very weak to me, and basically point to a “fail” of the fediverse in its own nature if threads joins. Kind of disappointing.

To me, the key idea of the fediverse is that it’s federated and should work as a whole, no matter who joins. Most of the answers below support the opposite. They are basically saying that the fediverse should stay within the “fediverse”, which is exactly what non-federated social media are doing. Meh.

Aside from the “moral” argument, can someone ELI5 what harm can a federated threads.net do on other users (like me) and/or instances?

I don’t think so, because forcing users to post means shitposting.

I can understand. After the initial excitement, the content is lacuster and scarse compared to reddit (due to lack of large userbase)