[halfbrite]

There's some subtle technical differences that would need to be overcome, and I cannot see the existing encumbents agreeing to those differences.

First, take private messaging - on Mastodon, if @alice and @dave talk about @mallory, @mallory will be pulled into the conversation. With Fidonet, in it's simplest terms, private messaging was private.

Second, if there is a forum / discussion board for / called Java on ProgrammerWoes.fiction and a forum / discussion board for / called Java on ProgrammerSuccess.fiction then with the existing solutions a person comes along and they are unsure which is better, and one eventually dies, or a third springs up, etc.

With Fidonet, there was one forum per topic - the contents of which was federated, so you didn't end up with two Java forums.

Yes, we have hundreds of programming forums - but there's a reason people flock to Twitter or more specifically Reddit to discuss a topic that goes beyond simply signal to noise - it's that they aren't flooded with a confusing choice.