We know, because Benedict has talked about his process, that he is a very thorough, precise actor. Every expression you see, every emotion you see in Sherlock, was intentional and planned by Ben. Nothing he does in an accident. Nothing you see on Sherlock’s face, or in his eyes, is there by chance.
Not only that, but when they chose the shots to put in the final cut of the show, these are the ones they chose. They chose these raw, emotional, close-ups of Sherlock’s face (not to mention the ones of John). We aren’t “reading something into it,” the love these two have for each other is deliberately, repeatedly, placed on the screen, by the actors, directors, writers, producers, editors, and everyone else involved.
(Source: hmsholmes, via bbcsherlockftw)