How does this compare to Mastodon/GNU social? From what I can tell, this is inviting me to run a P2P program on my own system rather than on a server; is that just an implementation detail?
What do you mean by this? Is there some sort of hardware politics battle in the GNU social community or something?
In addition in works offline (including images). Many of us catch up with friends and reply to their posts when on the train, plain, boat, road, whatever and sync up when we get to a net connection, or local connection to a local friend with SSB.