We're getting back to the issue of 'usability' though.

My desktop has no phone number, my tablet has no phone number and .. I have multiple phones, which have different phone numbers. I would like to use a single IM account (hey, like with mail. Or xmpp).

TextSecure doesn't allow that. TextSecure is not usable in these scenarios. It's not about "Could TextSecure leak my number", it's more about "The current architecture of TextSecure makes no sense for these use cases and seems to be quite close to WhatsApp et al - even before their agreement".

A telephone number is not an identifier, it's not stable and it's not something you can expect as 'given'. This is a broken system. As 13, the thread starter, mentioned.

You keep talking about "discovery".

I don't want to be discovered.

I don't want my Signal identity to be tied to any phone number.

I think that I'd be happier with social-network discovery: I can see my friends, and those of their friends whom they have shared with me; I can then ask to become friends with those whom I know, and then see their friends, and so forth. My namespace would be local to me, but I could browse my friends' namespaces as well.

You can install Signal on a WiFi-only iPad and use any phone number to register. This will also be the case for the upcoming desktop client.

I don't want to get any number. I want to have any number of throw-away accounts active in parallel on every device.

Just as with jabber, e-mail, IRC and every other open messaging technology.

Which you can only do in the US.