alt Hacker NewsI agree. There should be a hierarchy of intimacy, as it were, in order to initiate a friendship.
* Tapping Phones * Confirming Phone Number * Confirming Email * Connected via Other Platforms (Facebook, Twitter, BlueSky, etc)
As far as maintaining a friendship by tapping phones, again, I would make the friendships a constant and graph / rank intimacy by how often you tap phones as well as how connected you are to your friend (phone, email, connections on other networks).
I love the idea of hierarchy of intimacy, that is a great concept/phrase.
I'd make it so you could tap a phone, you know their phone number, you know their email. Importantly in my eyes, you shouldn't be able to navigate to a profile and just ask to connect as that'd mean you could do that to people you don't actually know (whereby knowing is inferred by you knowing some amount of their personal info such as tap, phone, email).
I'd stay away from your last option of 'other platforms', per my other reply below in that those platforms allow you to connect to anyone/anything. There is nothing in them that say this connection is inherently personal vs being generic.