As of more recently:

• The identity system is still the same, keys aren’t rotatable and still the core of your account. Outside of edge cases like Frost Bunkers (outsourcing key management to a cluster of third party servers), or platforms like DiVine letting you register with an email, keys remain pretty much the same.
• Private infomration like DMs have been altered. They’re still E2E encrypted, but now only the people involved in the conversation can request a copy of the encrypted DM (I assume that’s what you’re referring to, but I may be mistaken).
• Media attachements are usually uploaded to Blossom servers now. Standard notes still only embed remote media, but the ecosystem has a semi decentralized means of hosting content, and most clients will have a more standard ‘upload and share’ type of feature that most other platforms/protocols have.
• The more recent outbox model (on supported clients) allows you to set the relays that will host your content and replies/reactions to your content, diversifying the ecosystem away from a handful of big relays. Software like Ditto also provides a more Mastodon community style experience - even to the extent of supporting the Mastodon API.

The identity management is a big one. I’ve had my ActivityPub account get nuked when Nerdica offline, and my current ActivityPub server (Trom) is sometimes slow and misses remote events. Having an identity I control means that I don’t get my account nuked if something breaks, and I can participate within communities without being tied to their infrastrucure if the community is great while their infrastructure is not. It also works across different forms of servers - no needing accounts on Mastodon, Pixelfed, Writefreely, and Peertube in order to experience each form of social media on the network - on Nostr I can just use my same account across the network. It also makes me more tempted to host my own infrastructure, since if I get a case of the stupids, I can’t accidentally nuke my account.

I also like the protocol’s simplicity. It’s pretty lightweight, and pretty easy to extend with some custom code. While custom extentions would break normal stuff (adding custom stuff to shortform posts is just going to make your stuff not work with other people’s clients), creating something like a chess app or geocaching app is pretty easy. Even if said apps wouldn’t work with your standard shortform or longform clients, they’d still interact with other apps using the same custom code, and be useable with a standard account.

And, while I seem to be a minority in this thread, I also like the moderation structure of Nostr. There’s a few different ways to approach that:

• I use Nostr like RSS, I follow people I like and see their content - and I moderate it like I ‘moderate’ an RSS feed, i.e. choosing who I do and don’t want to see.
• There are other ways to moderate though, for example, by pulling people you follow from the whole network while only setting your global feed (if your client supports a global feed) to pull from specific relays.
• Or you could use something like Ditto, which is a Nostr relay behind a Mastodon front end. Ditto gives users a local feed and global feed (though I beleive both can be enabled or disabled), with the content on the Ditto server being capable of moderating content in the exact same way any Activity Pub server can (including accessing content or controlling moderation via the Mastodon API).
• Last, if I was famous or had people trying to spam me, I could also set my inbox relay (place where people send their replies on outbox model supported clients) to a relay I control, then set rules/filters on who’s allowed to reply and/or what content replies could contain.

Cool. Looks about right to me, not that I’m an expert. Bridgy Fed and Mostr do allow you to chain them together and do Nostr <> AT communication (though more recently there’s also Eclipse.Pub that does Nostr <> AT). There are also a few other protocols still in use (Diaspora, DFRN, Zot, Nomad - Diaspora, Friendica, Hubzilla, Streams respectively) although all but Diaspora all internally bridge to Activity Pub so I’m not sure how they’d fit into your model.

I’m kind of the oppisite in that I prefer Nostr over ActivityPub, but both have their merits. As for technical ways Activity Pub has a leg up:

• Comunities - Activity Pub is built around individual instances, with people able to join communities focused on their interests and/or that have their preferred moderation policies. Some software exists to do similar things on Nostr, but that’s not what most people use.
• Platforms - In a similar vein, Activity Pub is probably easier to make a platform out of, be it Meta making Threads or you making your own social media service for your friends. On Nostr people’s accounts exist outside of the infrastructure they use, so it’d be hard to provide a more unified experience.
• Ease of Use - Activity Pub generally has a lower technical barrier to entry, you can sign up with an email and a password on most servers. Outside of (upcoming) DiVine or using Frost Bunkers, there’s really no easy way to join Nostr without learning how to manage keys.
• Standardization - Acitivity Pub has existed for the better part of a decade, and the protocol hasn’t changed much for a while. Nostr is not only newer, but breaks it’s functionality into various NIPs (rules on how to interpret posts of specific types, e.g. shortform text, longform text, livestreams, etc) of which there’s 100+ official ones (and plenty of unnofocial ones).

There’s a couple different implementations that might be interesting to cover, depending on what you had in mind:

Friendica, Hubzilla, and Streams all support Activity Pub but focus more on a Facebook style social media instead of a standard microblogging platform.

Writefreely, Plume, Wordpress (via plugin), and Ghost (via plugin) all support activity pub and focus on long form content.

Peertube focuses on longform video, Loops on shortform video, and Funkwhale on audio based content.

There’s also bridges from Activity Pub to AT (Bluesky) and Nostr as well.