In practice, people invite strangers to talk to them on Deltachat.
Some post a point-of-contact profile publicly (example, point 5), then use another profile for actual conversations.
Would it be possible, when the new multi-transport identities roll out, to automate this? As long as a QR code is active, it has an attached transient account; when a contact is accepted, it could be transferred to the permanent account. This could tie into QR code deactivation management.