[troyjfarrell]

I don't think I understand how this is not circular reasoning (can't use UUIDs in place of phone numbers because contact list is comprised of phone numbers instead of UUIDs.) If contacts are not phone numbers, then is there a problem with them living on Signal's servers? Are we back to the complaint about discovery being difficult?

Signal uses phone numbers because it makes discovery easy. Threema, for example, can use phone numbers for discovery but does not require it. Discovery without phone numbers is easy. I see my contacts and scan their Threema QR codes. If I need to contact a friend of a friend, my friend gives me the FoaF's Threema ID.