Actually, E2E does end up being really important in Matrix because room history gets synchronised across all the participating users in a room. So assuming you

Actually, E2E does end up being really important in Matrix because room history gets synchronised across all the participating users in a room. So assuming you have /any/ non-local users in the room, they'll end up storing a copy of the conversation in plaintext-equivalent on their servers unless you have E2E, which rapidly becomes non-desirable for any private rooms given you don't want to have to trust everyone's sysadmins. And given 'run your own server' is half the joy of Matrix, we don't want to tell people to turn off federation if they want security! This is why we've made a real effort with Olm & Megolm (http://matrix.org/git/olm/about/ http://matrix.org/git/olm/about/) in Matrix to ensure that E2E is there in the baseline, and will be turned on by default for all private rooms. (disclaimer: I work on Matrix)