None of this could happen with a protocol. You cannot require age 
  verification on IRC, XMPP, ActivityPub, Nostr, or Matrix, because there is no 
  single entity to compel. Each server operator makes their own decisions. A 
  government would need to individually pressure thousands of independent 
  operators across dozens of jurisdictions, which is a legislative and 
  enforcement impossibility. And even if one server complied, users would 
  simply move to another.
  

The interesting thing about Nostr (vs each of the other options listed here) is that it works perfectly fine over sneakernet. And that has been impossible to block throughout the world, even in some of the most oppressive nations.

Since the spec includes identity, content (in multiple formats), and authenticity/integrity, this makes it superior to nearly all alternatives for offline use. Once you know someone’s key, you can verify that content comes from them, however you manage to obtain that content.