This is one of my favorite expressions in the whole series.
Sherlock is seeing just how hurt and isolated John is at this moment. And I love that John’s comment is bitter and snarky, but you don’t really know just from what he says how deep it runs. It’s Sherlock’s look here that lets you know how much John is really hurting. (And god, they play off each other so beautifully.)
And I love that some of John’s pain is Sherlock’s fault, and Sherlock’s recognizing that. And some of it is John lashing out at Sherlock even though it’s not Sherlock’s fault.
And I think Sherlock was braced for that, going into this whole confrontation, I think that—well, that and him re-injuring himself—is why he seems a bit tense and coiled-up through this scene. Sherlock isn’t going into this with no horses in the race. He does have something to lose. He could alienate John. And the careful way he draws parallels between himself and Mary, the way he basically is saying, “We’re alike, we do the same things, we do the same things to you, and you love the same things about us”—it’s a technique that could, on the one hand, calm John down from his anger with Mary and steer him back to focusing on the things he loves about her, but on the other hand, it could transfer John’s anger at Mary back toward Sherlock. John’s unlikely to simply write Sherlock off at this point, after what they’ve already gone through this season, but he’s got plenty of reason to be furious, and if anything was likely to bring that skeleton back out of the closet, it was this moment right here.
All of which is amazing. And yet it’s still not as amazing as the love and empathy and exasperation and resignation in Sherlock’s look toward John right there. It’s one of those looks where you can tell he’s seeing his friend so clearly. <3