Dembele pats him on the back. We’re done. Their interaction there corresponds with the general cordiality between the two squads during that match.
Also, and I assume related to this particular review process, they soon went to water break and Mbappe and Tello had a chat, which ended with Mbappe giving a thumbs up.
It's hard to overstate how common lip reading is at this level. So even if you wanted to tell a joke or off hand comment to someone you know, I could imagine someone covering their mouth.
I'm sorry, I was told quite confidently by people on the Internet that the only reason a player could cover their mouth is because they're saying something heinous and awful.
Stick with “dived” rather than “dove” if you want—I do. In high school in the U.S. Midwest some 60 years ago, I was taught that “dived” is the correct past tense of “dive.” The all-knowing Internet tells me that some 200 years ago, “dived” was the usual form in both Britain and North America. “Dove” has since become far more common in North America but is seldom used in Britain. I also frequently use em dashes—without remorse.