I think Urbit solves some of the issues that remain unsolved in Scuttlebutt. When you have non-zero cost NFTs as IDs on the network you make spam a non-issue and moderation 'easy'.

Avoiding blockchain in the actual system design also gets rid of the storage-intensive protocol issue, it's my favorite approach of the attempts to pull off these decentralized systems. It's also the only one I thing could truly work at scale as a new underlying system that applications can be built on top of from those I've seen.

The ability to update code across the network and the built in incentives for infrastructure nodes (stars) are really interesting. I also think the functional OS design is pretty cool.