Comment Re:Deflection? (Score 1) 59
It is more general than that, Signal does everything it can to get people in contact. In particular, it will notify you when one of your contacts join Signal. You can disable this, but it is not the default. It is significant, as it can reveal information you may not want to reveal. You may not want to tell your contact that you have joined signal. Of course, there is also the massive issue that you are using a phone number to join.
I understand why they do this, they want as many people as they can on their platform, and there are good reasons for that. But it is still a convenience/security tradeoff, one that is fine for everyday use, but probably inappropriate for classified conversation. Technically, Signal do the best they can, but they are still targeting the general public, there is no gatekeeping, quite the opposite in fact.
A modified version of Signal on a private server not using phone numbers would work, but not the actual Signal app. Or maybe Matrix.