Lemmy is "uncensorable" and offers identical moderation abilities in the "public square" aspect. E-mail is "uncensorable". Uncensorable does not equal unmoderated. It means if you want to publish something, nobody, not the even the government, can stop you (though they can throw you in prison but that's outside the discussion of protocol). It doesn't mean anybody has to choose to listen to what you publish. It does not mean relays have to include you in their list of public tweets. Relays can pick what tweets/etc they show. They can choose what goes through their relay. What they can't do is stop you and another user from using the protocol to DM each other. As long as one relay allows your traffic through, the traffic will flow. They also can't stop you from tweeting, they can just choose not to show your tweets. If I want to follow somebody, frankly, it should be no business of a relay operator or the government or anybody to prevent me from following them, just like it should not be the business of the government to decide what books I am legally allowed to read. By building networks which are "uncensorable" we can guarantee that it remains not their business for future generations. So that they can live as free, or freer, than we do.

The internet, as a structure, is "uncensorable". This is good. Power should be decentralized. The whim of a government shouldn't dictate how the entirety of the internet operates, and it can't. People in power love censorship, it is to their advantage that we are not able to organize among each other using common communication platforms.

Libertarians are not right-wing lmao

Still some of those, as with any social media platform. I have come across a few objectionable things, I just blocked and moved on. But you pick who you follow so you pick who shows up in your feeds. Each relay has their own moderation policies, so (like Lemmy), you can pick relays which suit your moderation preferences (which effect the "trending notes"/public square section). Most nostr apps by default upon install will ask you if you want to automatically filter out crypto/nsfw/foul language/etc. I picked at random and didn't enable many of the filters.

Nostr isn't a Lemmy alternative, it's a Mastodon/Twitter/BlueSky substitute with more decentralized, secure and private features and i think OP should have pointed that out.

And since Op was comparing the secure and private features of both protocols, ActivityPub surely has improvements to implement for greater privacy and security.

DMs aren't as relevant in Lemmy so I get why securing them isn't a priority, but in Mastodon or any twitter clone it seems like a relevant feature I'd like to have some security/privacy with. Instance admins, and anybody who breaks into their server, being able to see all DMs seems like a security flaw that should be engineered away. Even Facebook, the place with the worst privacy, has E2E encryption (or so they claim, who really knows)

Lemmy is absolute garbage on privacy

I mean, yeah, it is. But that's because privacy is not what it's trying to do. If anything, privacy is fundamentally antithetical to what it does. Saying "Lemmy is garbage on privacy" is a bit like saying "Microsoft Word is a terrible IDE".