Private posts is something I’d like to have too. In WP it is possible, by having posts you need a login for. Finding a way to smooth that, which doesn’t require me to have other people having an account here, would be great. Automating IndieAuth access looks like a viable path.
However, private posts is just a first step in my mind. On my wish list is a deeper form of allowing selective publishing: private elements in otherwise public postings. Where one site visitor might read ‘my daughter’, friend might read her name. Where other read ‘a client’, colleagues would read the organisation’s name. Building a smooth spectrum from fully public to fully private. Along the lines of how we in conversations also continuously switch between different degrees of disclosure, and not just between conversations.