Molly is the exception. Not only is she in his heart, but she is a vital figure in his mind palace. Just this once, Sherlock broke his rule. And just as she's done so many times before, Molly Hooper saved his life. >>For the caption
And when Molly tried to imply he only cared about John's opinions/concerns he quickly let her know she always counted too. So all we've really learned from this is, when pressed, he will be considerate of peoples emotions.
I dunno what would happen actually. Would just live as if nothing happened, or would he lose it and go serial killer? << I'd unfortunately vote serial killer. Or lots of drugs. Dear god thank you for not doing it John