E2E usually suffers from the same thing HTTP does: the MITM might not be able to read what you’re saying, but they know who you’re saying it to, and they may know in what context. This is a lot of information that can be used in profiling.

So you end up with systems like SimpleX, where everyone has a different UID for every contact, but that has its own problems, as anyone who’s used systems like that are aware. We haven’t really solved making that a good user experience for messaging; I don’t see it translating to broader social media any time soon.

Nostr has some really good specs and tooling that neatly addresses these topics, including great cryptography support, signing, ad-hoc IDs, and an entirely voluntary simple naming lookup; it doesn’t exactly solve zooko’s triangle, but it provides a toolset sufficient to mix and match characteristics for whatever your threat model is. Sadly, Nostr is utterly dominated by the crypto crowd (and is associated with some controversial personalities), and even if you’re not cryptocurrency-hostile, it’s a really dull echo chamber with little other content that has prevented people who might otherwise build interesting platforms in it from doing so.

Mastodon was around for ages before (the in practice centralized) Bluesky; why did it take Bluesky to open a mass exodus from X?

This is a hard problem to solve. Throwing E2E at it doesn’t make it easier; it’s just tossing a buzzword in.