Right. I had to tell this to someone the other day when they pulled an "I was only kidding"...
If you have to explain the joke, it's not funny.
But if you have to tell the other person that it was a joke, then it wasn't.
But Angus was joking. I saw it that way. A little lame, yes, but sparring right along. The problem was Faye's reaction face - I think she's got way too much emotional investment here for that joke. Somehow, it got too close to a truth for her (probably that same boyfriend), and she got taken aback.
The only thing Angus could or should have said to that face was a quick apology, then let it pass.
I'm prety sure that's not in his repertoire, though!
Oh, and Binary? That's her left hand on the table, not her right. The forearm's hidden by the table and her body. All's well.