

I mean, what is actually needed is a secure messaging app that scrapes wraps existing apps. So when two people send messages through FancyMessages, they are secure. But then if only one person has FancyMessages, and the other has Facebook messenger, then they could still comminicate - the FB user using Messenger as usual, and our hero’s FancyMessages app picking up the FB messages and passing them on through the FancyMessages UI.
I mean, this is a valid point, but framed negatively.