Here's my experience. I have three devices I use to connect to my XMPP server: phone (Conversations), PC and laptop (both gajim). Each one generates a keypair. I verified the public keys of PC and laptop by scanning a QR code using Conversations (phone). Conversations remembers all fingerprints as my own. Next time I meet a friend, they scan the QR code on my phone. They now have verified all three of my devices.
What do you mean by that? When no new devices are introduced you only have to verify the fingerprint of each contact once (via QR code).
> Afaik it does not have any audit either
https://conversations.im/omemo/audit.pdf