I am deaf and fluent in American Sign Language. I teach ASL courses as an adjunct professor at a local Christian university. I think the skater is a hearing person, with knowledge of Brazilian sign language. Many hearing people have learned sign language.
Vapor trails. I've flown in a 747 at 39,000 feet and walked over to the very last window near the tail section and observed 747's engines hot exhaust. I saw vapor trails.