Delta chat looks great, and reusing the existing infra is a huge boon. However, it has the same issue of hard reliance on a specific server for connectivity.

Why do every system insists on having persistent names as network identifiers? Practice shows that the main threat for the vast majority of users is state censorship. In case of Delta, Matrix, XMPP and others, once you're cut off your home server, your account is basically toast. The only thing you can do, besides circumventing, is a cumbersome and messy account migration[1], where available.

In case of Matrix, I feel very bitter, as I managed to onboard a considerable chunk of my personal network but most of them can't login anymore without using VPNs. I'm not sure if I have enough social capital to convince them to repeatedly register on different servers as they get blocked. P2P[2] feels still too far away.

Why can't we use key pairs as identifiers and simply request a desired username upon first login? In case of federated networks this would allow seamless server switching and allow users to continue their conversations. Servers shouldn't care what server a particular user's messages are coming from as long as they are verifiably theirs.

You can even add username propagation between servers (a new server requests the username from the old one that's supplied with user's login request). I know about Matrix identity servers but I don't see how it helps in this case.

1. https://ems.element.io/tools/matrix-migration

2. https://arewep2pyet.com/

agreed, lack of account portability in Matrix is a pain. we’re working on it in msc4014 and I expect to see some progress this year.