> In my case I can definitely relate to this for personal communications, I no longer send emails to personal acquaintances I think we can agree that they have

> In my case I can definitely relate to this for personal communications, I no longer send emails to personal acquaintances I think we can agree that they have different strengths, I haven't seen much change in my usage of email for chatting with personal acquaintances because email has never been going strong there, unlike Instant Messaging… > but a killer feature is way more efficient, especially in the long run …if one thing, popular IM of today pack less features, not more, than those they replaced. Remember the golden age of MSN messenger? You had whiteboards, tictactoe/chess/… games with friends, screen sharing, fancy fonts & colors, "now listening to:" , wizz, … Ironically, XMPP inherited all those features out of necessity to be compatible with all those protocols (and I don't think it matters the slightest). XMPP does have quite nice and unique features of its own, if check-out the other response :) > WA offered users a way to text using the same phone numbers for free in countries where you had to pay just like every other messenger then and now… (I'm not downplaying their coming ahead of this fierce competition, they must have done something right indeed, but "IM as a cheap alternatives to SMS" was popular a decade before WA) > WA also uses the Signal Protocol, which I assume is not directly compatible with OMEMO "Signal Protocol" is a mashup of encryption algorithms, signaling and session negotiation, at its very core there is the double-ratchet algorithm (for forward secrecy) and prekeys (for offline delivery), OMEMO is just that, implemented over XMPP primitives (with prekeys served over PubSub/PEP). > My point is that it's not as simple as setting COMPATIBLE=TRUE to make every network compatible with each other. Indeed, it would take some careful considerations, but eh, same can be said about TLS. At a first glance, I don't see anything radically difficult about it, the main point would probably be to offer a generic endpoint to serve prekeys and there's nothing revolutionary or difficult about that. > I doubt Facebook deviated from the base protocol just for the sake of it They did what every big business does: they optimized for their specific needs. When they decided that compatibility wasn't something they could monetize, they shut the gateway down and stopped caring about it. That tells nothing about the protocol, its capabilities, or of a presumed inability to extend it. For that matter, the X in XMPP stands for "eXtensible" protocol, and it's been quite good at keeping up for about 22 years, now :)