Wan's humor started to fade when R told him to hold on and he headed into the back room. It was completely gone by the time the other man got back.
He hadn't been surprised that Rene hadn't recognized him during his introduction - neither of them had seen the other in person. But he genuinely thought that the Gambit reference would be an immediate memory trigger. That the other man would join in on the laughter and they'd both feel good about it. An in-joke they shared.
But it was just Wan laughing. And when he laughed alone he wasn't laughing with anyone. He was laughing at someone. Which was something Wan didn't feel at all good about. He didn't want to be a bully. He didn't want to hurt someone like that.
When R returned, Wan had quieted completely. He was quiet, contrite, as he nodded at the entry, "Yes. Sorry for laughing. I thought you'd- doesn't matter. I shouldn't have laughed at you like that. Sorry. I can go if you want me to."