I tried setting it up with a friend this morning. I see a checkmark next to his name in iMessage, but he doesn’t see one next to mine.
When I look at his Contact card, both his phone and email are verified. When he looks at mine, only my email is verified, not my phone number. That would explain why I’m not Verified in his iMessage.
He also says that when he looks at his own Contact card, his email is Verified, but not his phone. When I look at my own contact card, nothing is Verified.
We first exchanged Verification Codes by email, then tried Verify Contact directly within iMessage, with the same result.
Clearly there are issues with Contact Key Verification.
EDIT: About an hour went by, and my friend’s checkmark disappeared in iMessage. I opened his Contact card, and his phone was no longer Verified. I edited his Contact to paste his Verification Code back in, and his phone was once again Verified. Also, I pasted my own Verification Code into my own Contact, and now I see Verified next to my info as well.