[Arathorn]

> For every other app in the world, the answer is that it lives in a server-side plaintext database. Snapchat, WhatsApp, Telegram, Matrix, Wire, FB Messenger, Skype, etc etc... they're all just storing your entire social graph in a plaintext database

This is true for today's Matrix network, but we do have peer-to-peer Matrix working now too (as previewed at https://fosdem.org/2020/schedule/event/dip_p2p_matrix/) which stores the metadata purely on the clients. There are no servers, other than rendezvous points to seed the network. (It's still vulnerable to traffic pattern analysis, but we're working on that - and Signal suffers this even more).

It's also worth noting that because Matrix doesn't tie identity to phone numbers (or anything else), the 'social graph' which is built up is of limited use if it's built up of anonymous personae.