Can you explain this a little more? Because the problem I see is that with any unique identifier it is hard to share in a hostile environment. Let's say I want to share my contact information to someone here but also share my contact information with someone on Reddit and not reveal that I am godelski on HN. Because if I use the identified "1234" here and "1234" on Reddit then I've connected those two accounts.

The only way I see it working out is with temporary identifiers or expiring links like FF send used to have. I saw some users talking about this in the community signal community form[0]. I agree with the users that are trying to say they want to use usernames to be anonymous, not as a way to hide a phone number.

[0] https://community.signalusers.org/t/usernames-in-signal