Comment by lvh

That's a fair point, but the fact that there's yet another protocol, not mentioned on the XMPP E2E wiki, kinda plays into the point itself: XMPP has E2E maybe with a bunch of random protocols and the stars (and the people you talk with) need to align _just right_ for all of it to work. I think it would be fair to say that everyone uses WhatsApp and I know what they get, and at this point only XMPP people use XMPP (explicitly) and maybe they get some kind of E2E but who knows which one and what properties that has.