For me it is quite different to Mastodon as it's not just a twitter replacement run on different servers.
It has entirely possible to run this completely without a server, so if in an isolated network, the local LAN could be your sole connection.
Then perhaps one person goes out to another town and connects to the internet, they collect many many messages from internet.
They then come back to the isolated network and connect, everyone gets the messages they collected. I have seen this effect happen when using both laptop client and mobile phone client.
When internet was down, my phone was able to get messages. Then it connected also to the wifi and my laptop (on the wifi) was not getting messages from internet; but got from my phone.
Spotted the site from the abstract for YAPC::EU. So gave it a go on a couple of my Perl projects.
Great stuff.
Looking forward to seeing the talk in Amsterdam.