Interesting take on blocking. Could be accomplished on nostr by only publishing to your relay and gatekeeping it. Blocking still isn't a real thing though, it's fiat nonsense.
Discussion
Mastodon has been trying to do privacy features like this forever. It's the reason they don't have quote posting yet. They want to limit who can reply to a post. Something that goes against the grain of decentralized social networks.
Does not change the fact that blocking is artificial and can easily be bypassed.
Reputation systems with Web of Trust > blocking
I’m a big fan of having private posts. Let people define a list of accounts that are given the key to their encrypted posts.