I was making a poorly informed assumption that signal's popularity must hinge on a key exchange process that can be MITM'd by authorities with enough privileges

I was making a poorly informed assumption that signal's popularity must hinge on a key exchange process that can be MITM'd by authorities with enough privileges on the network to setup a persistent interception operation that spans every access point on the target's network partition. So for instance, if you are using signal to do an outreach and support operation for a human rights group operating in China, it might be reasonable to assume that some Chinese intelligence orgs can view your plaintext. The strategy would then be to not transmit any information that would allow a decisive action against the group. The opportunity cost of revealing the surveillance has to be greater than the utility of acting on the intelligence. But obviously this would compromise the scope of assistance you could provide. And the risk is iffy, for a few reasons that I've thought of since seeing your response: 1) PGP key exchange has the same problems when done over the network. Doing foreign outreach via PGP has the same problems. 2) I don't know of any examples of Signal MITM attacks stemming from weak key exchange. Worse, I don't actually know how key exchange works on signal 4) Key exchange problems are more of a universal nitpick against all crypto systems, not a full compromise I'd be curious about your feedback - even if it's a chastisement. I am also curious if you feel signal has any REAL issues which keep you up at night, if not key exchange.