What exactly do you not buy? I think you might be missing the point on what is meant by discovery here. This is not about random strangers talking to you, but a

What exactly do you not buy? I think you might be missing the point on what is meant by discovery here. This is not about random strangers talking to you, but about the issue that you have signal, your friend has signal, but even though you're already in each others phone books you can't talk to each other because you haven't exchanged pseudonymous pointers. There are exactly two pseudonymous identifiers that have "made it". Both associated to technological revolutions. One is phone numbers, the other is email. You put them on business cards and save them in your contacts. This is strong evidence that this is a hard problem. No other identifiers have been successful long term. And yes, this absolutely prevents encrypted email adoption. Imagine if switching to encrypted was like installing signal (back in the SMS fall back days). It's: "Hey use this email client, it automatically detects when the person you're mailing also has an encryption capable client and then all your communication with that person is encrypted." vs. "Hey use this EMail client, and if you find out that someone you know is also using it, you can go to this menu item here and search this database in order to find out how to email them securely, and if that doesn't work just email them normally to get a public key from them, before you send them the document you wanted to send." No guarantee that the former would work, but it would have a fighting chance. Of course such a solution isn't possible partly due to usage patterns that email has that would break. But that's why I'm relatively forgiving of Signals strict stance on shooting down these type of feature requests. Because they actually have massively improved secure communication for more than a billion people.