We really don't want to become the next WhatsApp fwiw. The idea is more to be the new email, or the realtime version of the web. We should be able to support the use cases both for privacy enthusiasts as well as mums, dads, grandparents or whoever.
Do you imagine the new email is going to be anything like the old email, in allowing easy composition of substantial, letter-length messages which can be organized in their own right?
I would love to be able to point non-technical users to an email alternative with sane integrity properties, and I've tried to some extent to push correspondence to Riot, but as it is right now, many of those users seem to suffer from Riot's flat design and not adapting well to the room metaphor. And one trigger-happy composition line posted to infinity scroll chat is pretty far from the experience of even a rudmentary email client.
I'll admit I haven't done a thorough search of the clients but if you're aware of good implementations of a letter metaphor for Matrix I'd be very grateful to learn what I've been missing.
We don't have a good letter metaphor in Matrix yet, but it should be coming fairly soon - we have someone sponsoring development on threading, and so you should get that bit at least in the coming months.
However, the other aspect of mail style semantics is the incredible flexibility which email gives in terms of adding/removing people from threads on a message by message basis. This doesn't map very tidily into a Matrix room currently, and is a bit of an open question right now :)
I hope the Matrix equivalent will be able to fully match and outdo email eventually, but 1-on-1 is already enough to be valuable, and it seems to me the room metaphor should be possible to map fairly gracefully to mailing lists at least.
Thanks for the efforts, as always!
I will read up on more of the current capabilities soon, by the way, to see if we can put an society I'm in on Matrix for internal communications and event announcements.
