Hee hee! Of course Sherlock would leave his shirt off under his robe with no thought to the effect it would have on John. It's great to see our favorite detective duo up to some reading that isn't about their latest case.
Aww, they're so cute! It looks so natural, like something that might actually happen. Sherlock and Watson's relationship is a complicated one, I can't really see it as sexual or romantic but they're so inseparable and they're comfortable being affectionate with one other, such as cuddling, holding hands, and sleeping together (in a non-sexual way). They act in a way that makes it understandable that people mistake them as a couple. I think that's the way their relationship was originally supposed to be like and what makes them one of the most famous relationships in all of literature.