tbf, decentralisation + e2e crypto is hard, as we've discovered at Matrix & Riot. You can have some wonderfully nasty situations if you don't know which device

tbf, decentralisation + e2e crypto is hard, as we've discovered at Matrix & Riot. You can have some wonderfully nasty situations if you don't know which devices (or even users) are in a given room, because the room is by definition not globally consistent due to being decentralised. Although we're doggedly working through addressing all the edge cases which result; my guess is that it's about 6x more work than the equivalent centralised service.