At this point, it isn't clear why federation is in there at all. The "forums, bit twitter" concept does produce nice places, but federation seems like a net negative for that.

Federation is good if you want to stay within a community but also have a chance to interact with others.

I.e. you mostly care about technology foo but occasion delve into epic poetry, and it's nice to interact with both footech.social and epicpoems.read. Also, being able to consume personal publishing (blogs!) from within the same app is quite nice.

The steelman for federation is that email survived the rise of the big platforms despite no-one owning email, so making other applications follow the email model means they too could be free from central ownership.

You'd have to have a lot of trust that the one instance wouldn't get enshittified and end up as another X / Truth Social / BlueSky.

Different instances can also have different rules, different moderation and different federation.

Edit: and exist in different legal jurisdictions, and also be harder to ban or regulate.