This is great an all but it doesn't really address the big problem with end to end encrypted messaging. That would be the usability issue. There is no point in constantly designing new protocols if very few people will ever be able to use the resulting systems. We make these things and then wait for someone to come along and make them usable. That never seems to happen.

I think we really have to turn things around the other way. First determine what a usable system would look like and then only after that is determined start thinking about the cryptography that would work for that system. After all, the cryptography aspect seems to be the relatively easy problem. We solve it over and over again.