There's a lot to like about @matrix , but I just tried to DM someone and it took several hours(!) before they 'joined' the 'DM room' and I could start writing... yeah there's some way to go. (we were both using :matrix.org accounts)
@raboof huh that delay in joining is waiting for them to accept the invite? and you can already send messages that they'll see after accepting
@f0x ah - I was sure I remembered someone not seeing the messages I sent before they accepted the invite, but looking back that was due to "problems with encryption keys", indeed not a 'general' problem.
Then I guess my 'actual' criticism should be that all this isn't very clear in the UI (I'm using element-desktop) :D
@raboof yeah.. it should totally have a little banner there that you can already send stuff for them to see when accepting
@f0x https://github.com/matrix-org/matrix-react-sdk/pull/7998/files - though I see there's some ceremony to complete before this PR meets all requirements... something for later ;)