[TuringTest]

But tying accounts to instances, and then instances to topics, is bad design. The purpose of multiple accounts from a user perspective should be for having separate identities, not separate topics of conversation.

If you're forced to create one account per instance, there's no way to do something as simple as "merge comments from two instances into a single stream", which supposedly was the selling point of federated systems like Mastodon.

[WorldMaker]

I'm of the opinion that tying instances to topics is the mistake here. Since the software is mostly following the email provider model, I think it makes more sense to base instances along other lines of trust model/ownership model/hosting provider than "topics".

Obviously "topic" is the easiest way to differentiate instances today, but when was the last time you choose an email provider based on "topic" (or even domain name, for that matter)?