To clarify, private circles (which all circles are by default) do not federate, and shared circles currently don't either (though the circle feed and member list can be viewed by people who aren't a user of your instance if shared publically). We're looking at Mastodon's draft proposal (starter packs FEP) as a way to potentially federated shared circles in the future though: https://github.com/mastodon/featured_collections

@ivan @johannab @LiquidParasyte ​