I should use this as a strong argument for the rest of my no-please-not-another-instant-messenger-i-stay-with-whatsapp-contacts:
When whatsapp is implementing the signal protocol, why should one use whatsapp in the first place?[1]
I hope this good advertisement gives signal another round of traction.
[1] Ok, you've got me. The less techie contacts will swing the feature-bat and the other already use signal.