By using signed objects the mechanics of fep-1b12 should extend to activities only addressed to the group. This will lead to “facebook style groups”, i.e. only members of the group can see what was posted to the group.
This might require some UI work in implementations:
- It should be possible to address a post to a group. The Mastodon mechanic of “mention” + selecting visibility “mentioned people only” might work in theory, but would lead to users unhappy with the UX if they are supposed to use this for group posting.
- Announce activities from a group need to interpreted correctly, in particular one should be able to reply with the group being the recipient.
I don’t think any of this is hard. It just needs thinking things through properly.