Question: Technical reason for private instance and federation being mutually exclusive?

[Algebro7]

Question

I ran into the problem "fixed" by #3074 yesterday and I was curious...why can't private instances federate? Is it a requirement of the federation protocol somehow? And if so, is there a way to work around it?

Use case: I run a single user instance where I don't create any of my own communities but I subscribe to and interact with a variety of communities on other instances. By making my instance non-private, everyone on the Internet can browse to it and see every remote community I've looked at which seems pretty bad for privacy.

I'm guessing this is a requirement for the federation protocol but I'm wondering if it is actually necessary to disclose the remote communities an instance user has subscribed to. It seems logical that other instances would need to know about the communities on an instance but since these are all remote, I'm not sure why it would need to know about those. Can anyone help me understand this technical aspect of Lemmy?

Thanks!

[Nutomic]

Its because Lemmy currently treats all communities and posts as public. So if you had a private instance with federation enabled, the communities could still be accessed over federation. Fixing this would require support for private communities.