It would be wonderful

To do something like this. You would need to be able to grant access to follow and be able to revoke access to follow. I can imagine two methods. 1) A kind of encrypted message where only those with the rotating “secret” can read the post. And only send to those you want to send the rotating secret. It would either need to be a single secret for all, or a unique secret for each npub. The groups spec wrestles with these dynamics. But you could create a private group for yourself and grant/revoke to the group. 2) Set up a relay, post only to that relay and whitelist the npubs you want to be able to read notes from that relay with a list you maintain. I recommend this approach. It can be implemented right now, unilaterally, and will work with all clients and message kinds. It doesn’t require any client or devs to do anything you can control this right now. A third option would be to just change your relays or use paid relays. If you share a relay with a harraser or a spam bot. Then you will see their notes and they will see yours. If you don’t have relays in common then they won’t. So using private relays will cut down on spam and perhaps harassers. Each relay is like a private club. You post notes and read notes at the relays pleasure. You can post to and read from many relays. You only have full control if you run your own relay. This is my understanding.