He still thinks out loud even if the room is empty of anyone to hear. It's a different room now, and he is a world away from the one containing ears, but he likes to think he can still be heard. Unrealistic yes, sentimental definitely, it helps him to think, he rationalises but he isn't entirely sure that that is true.
There were very few people Sherlock took the time to explain his thought processes to. The look of mesmerised wonder on the ex-army mans face always warmed his insides in a way he could never really remember experiencing before. He was like a small child watching as the masked magician pulled yet another rabbit out of the hat. Sherlock was long since jaded to the predictable reactions of others (Piss off. Freak. Liar) that perhaps this was why the shining smile of the very ordinary former doctor had caught his heart.
Like you have a heart? Not his own musings, or the words of John, who somehow saw right through him, but rest of the worlds. And perhaps to an outsider this may appear to be true. Cold, calculating. A robot. But in truth, the heart of Sherlock Holmes was the worlds most guarded secret. His body thrummed with the biological enzymes and hormones much like any other. He understood the true science of "feelings" thoroughly, but little of the meaning. As a small child he had closed himself off. If he didn't cry they wouldn't call him names. And later he learned the true power in this skill he had developed over time.
As a sociopath, it was difficult for Sherlock to maintain any sort of relationship. But then there had been John. Simple minded John. Caring John. Almost empathic John. John who had distinctly average deduction skills, yet could undo the mysteries of Sherlocks emotional state with a glance. John who looked at him and saw something other than the monster he thought himself to be. John, who he would watch when he knew he couldn't be seen. Not cataloguing, or prying or trying to unravel any sort of anything. The answer was simple enough. When he caught his own reflection in the other mans eyes, he saw himself how his friend saw him. He liked it. He hoped one day that he could be that man. And it was that reason alone that Sherlock spoke out loud to an empty room many hundreds of miles from Baker Street. It was the only way he could remember that warmth, and hoped his frozen insides would feel it again.