In AP, messages are signed with http signatures (https://tools.ietf.org/html/draft-cavage-http-signatures-09). OStatus has a similar mechanism called salmons, which are signed XML payloads.
The ideas about using DID's (https://w3c-ccg.github.io/did-spec/) and moving off a common transport like HTTP was also interesting.
If building the next version of internet discussion and sharing, we really need first-class support for encryption.
If my personal twitter-style communication got out it would be worse to me than my more private messages, but it is worse to me personally if all the twitter style communication gets out than only my more private messages.
You have to account for manipulative big data risks in your analysis, thinking only about your personal data is an outdated approach.
Doing it the other way around? We literally have 50 years of experience of that being a terrible, terrible idea.