Second, there's an in-between kind of audience -- a set of people that I don't know personally, but that I trust some smart moderators have vetted. Bike lovers, Montreal Open Source fans, ActivityPub developers. Sometimes you want to talk to "people like us", vaguely defined. Facebook Groups work like this, for instance; well-managed mailing lists and chat groups work this way, too. My hope is that the work that we're doing for groups in the SocialCG will help with this: https://github.com/swicg/groups
Finally, there's that extra step of end-to-end encryption (E2EE) that protects the content even from your (and their) server operator. I think the current work on bringing MLS to ActivityPub will help with that a lot. https://github.com/swicg/activitypub-e2ee
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