Are you basing your argument on assumptions that: A) Most contacts have phone numbers B) Most contacts don't have email addresses? I think you're assuming

Are you basing your argument on assumptions that: A) Most contacts have phone numbers B) Most contacts don't have email addresses? I think you're assuming this (and as it happens, I agree, although the number of email-only contacts is still nonzero for a lot of people). Are you also assuming that it just adds a lot of complexity to be willing to search by both phone numbers and emails? That's the part of your argument I'm not grasping. Signal has to be willing to intersect known-account-identifiers with this-device's-local-contact-handles, what's the problem with preferring phone numbers but allowing emails?