@smokey I think you’re right that this part of the identity piece hasn’t been figured out well within the broader IndieWeb. There is a broader idea of “publics” that covers some of what you’re talking about. I suspect that @kevinmarks has written about it extensively in the past if you’re looking for some general guidance. Some of the other relevant pieces I’m aware of are those of “audience” and several have played around with the idea of private webmentions as well, though these have yet to be built out to enter the mainstream yet.
On my personal website I have several friends and family who have access to various private areas which they can only read and comment on while logged in, so it’s a small start, but isn’t nearly as flexible as one might wish.
I suspect that as things progress and laws like GDPR require more of it, these ideas will become larger itches for more people so that they can maintain just one website which only reveals the facets they want and only to the audiences they want.
Thanks for re-raising the issue. We definitely need more people thinking about and working on it.