I really love signal and I, too, fully agree with this sentiment.

I have managed to keep a phone number for almost double-digit years. It would be amazing to not have to use my telco as the source of identity for my Signal communications. If Signal could change this one thing and allow (or maybe somehow prefer?) it to be linked to a mobile number it would have real feature advantages over all of the other random chat apps for phones. Signal call quality is jaw droppingly good, but thats hard to sell at the gas station or water cooler.

As it stands people I refer to Signal usually have a preferred chat app (which is unfortunately often facebook messenger) or SMS. IOS people have no reason to use it other than the amazing privacy benefits, and android people seem to be on whatever their mom isn't.

I would pay to not have to use my phone number for this service.

You think making contact discovery much more difficult for people will make them more likely to select Signal as their preferred chat app? Especially if you are asking them to replace Facebook Messenger. If they are willing to message people using their real name, I don't think hiding their phone number from them will be a great draw.

I totally agree, but I also totally disagree that supporting this alternate use case will make the app worse for naive, regular users to discover their grandma is on Signal.

Im asking for an alternative canonical source of identity other than an extremely trustworthy telco.

Some other conglomerated examples are: Scanning a QR code in person to initiate discovery, or querying other data in the phone's "contacts" PIM app for example, email, or more imaginatively, keybase, or maybe mail out QR codes to residential address for a nominal fee?

If could be very relevant for journalists in general. I wonder if they just use burner phones in conjunction with it