Initially they were there to offer richer error messages when the wrong
code was scanned.
However, we found that people were posting them publicly,
misunderstanding the QR codes to be a kind of personal identifier.
For one, this isn't useful because the QR codes, like safety numbers,
are unique *per* conversation. So they aren't useful in a generic sense.
And secondly this is bad because the QR code contains both parties phone
numbers.
// FREEBIE
In coordination with Desktop and Android, iOS will be using all-numeric
fingerprints, aka "Safety Numbers".
Furthermore, the concept of verifying one identity and then the other
has been removed. Instead we ask users to exchange a single number, or
scan a single QR code. These credentials are built by combining the
users identities.
// FREEBIE
