Is John trying to prove he’s not gay?
This is the picture Molly made Sherlock pose for as an apology to her for his earlier debacle. ”And you will smile like you mean it.”
John’s hand isn’t actually touching her; he was captured in mid-unfortunate gesture. But what the heck, he’s cute and it foments her fantasies of a threesome, so when he was like, “Oh, god, let’s take that picture again,” she said, “No! No, that’s fine, it’s…funny! It’ll help me remember the moment.”