Thank you so much!! :)
Apparently I’m incapable of answering this kind of thing without turning it into a full-blown meta. Let’s just look at the whole scene, because it’s funny, but (as always) the humor is masking quite a bit of darkness.
(transcript credit here)
MOLLY: What is it?
(Sherlock gets his phone out and holds it up high to try and get a signal.)
MOLLY: You’re on to something, aren’t you?
SHERLOCK: Mm, maybe.
This one’s obvious. John calls Sherlock a “show off” frequently. But next time you watch this scene, listen to the tone of John’s voice in Sherlock’s head. It’s harsh, insulting. It’s not the same tone Real John uses when he tells him to stop showing off. So why does Sherlock hear it this way?
Because despite his arrogance, Sherlock’s self-esteem is actually crap. In fact, that actually explains the arrogance – after all, arrogance is not always a matter of overconfidence. Sometimes it’s the opposite of confidence. When John says stuff about the showing off thing or being all mysterious with your cheekbones and turning up your collar so you look cool, Sherlock hears the words but he fails to understand the truth behind them, the real reason John says this stuff:
It’s what John likes.
He likes the showing off. Fantastic! (Do you know you do that out loud?) Sorry, I’ll shut up. (No, it’s…fine.)
John loves watching Sherlock show off, and Sherlock loves showing off for John. But of course, John isn’t going to act like a simpering fanboy on the outside, nor will Sherlock openly acknowledge how much he loves basking in the attention. These are two men who have a lifelong habit of suppressing those types of emotions. Unfortunately, the hard exteriors they’ve built are so damn near impenetrable, they even manage to fool one another.
So John doesn’t realize Sherlock shows off for him just because he craves John’s appreciation and attention and approval. John doesn’t realize he’s special. He only sees the exterior; he thinks Sherlock’s an arrogant show off.
And Sherlock doesn’t realize John’s sarcasm is just a mask for the frustration and confusion he’s experiencing due to the effects the showing off and the cheekbones and the being all mysterious have on him. Sherlock doesn’t realize he’s special. He only sees the exterior; he thinks John’s irritated by his act.
That’s what we’re hearing in Sherlock’s head right now. Not real John, who actually loves watching Sherlock deduce. These are his words, but spoken the way Sherlock interprets them, rather than the way John means them.
SHERLOCK: Shut up, John.
SHERLOCK: Hmm? Nothing.
LESTRADE (glancing towards Molly): This gonna be your new arrangement, is it?
SHERLOCK: Just giving it a go.
LESTRADE: Right. So, John?
SHERLOCK: Not really in the picture any more.
(He moves away from the table and turns back to look at the whole picture. Cement dust drifts down from the ceiling as a distant rumbling can be heard.)
Right, John’s out of the picture. And Sherlock hears the distant rumble of unseen trains. Nothing subtextual to see here, move along…
MOLLY: Male, forty to fifty. Ooh, sorry, did you want to be …?
SHERLOCK: Er, no, please. Be my guest.
Molly makes this deduction first. She beats him to it. Jealous, Sherlock?
SHERLOCK (angrily, through gritted teeth): Shut up!
LESTRADE: “How I Did It” by Jack the Ripper?!
MOLLY: It’s impossible!
SHERLOCK: Welcome to my world.
SHERLOCK (quietly, through clenched teeth): Get out.
This scene isn’t just about Sherlock missing John. It’s about just how fucked up Sherlock’s head and heart are right now. John refuses to forgive him, and Sherlock’s beginning to understand just how much he hurt him. He screwed up the fall. He screwed up the return.
Low self-esteem + guilt = self-loathing.
That’s why John’s voice is so harsh, why even the text appears different than it does with normal deductions – fast, sharp, fiery. The words are like bullets and Sherlock’s exterior is starting to crack.
He’s still trying to keep up the act, though.
SHERLOCK: I won’t insult your intelligence by explaining it to you.
LESTRADE: No, please – insult away!
That’s right, do your little trick for the ordinary people, and don’t forget to look all cool and mysterious as you do it.
SHERLOCK: The-the-the corpse is-is six months old; it’s dressed in a shoddy Victorian outfit from a museum. It’s been displayed on a dummy for many years in a case facing south-east judging from the fading of the fabric. It was sold off in a fire-damage sale … (he gets his phone out and shows the screen to Greg) … a week ago.
LESTRADE: So the whole thing was a fake.
LESTRADE: Looked so promising.
MOLLY: Why would someone go to all that trouble?
SHERLOCK (offscreen): Why indeed, John?
Cue his shadow slipping through the busted, fragmented, splintered door.
If you ever hear anyone complain that Woobie!Sherlock in TSoT was unexpected, that him working so hard on planning John’s wedding was OOC, that his brain meltdown upon learning that John considered him his best man and his best friend didn’t make sense, then refer them to this scene.
Because this is when we start to see Sherlock truly believes he’s nothing more than a world-class fuck-up, and that’s how John sees him too. His exterior is pretty much shattered, and in TSoT, the real Sherlock is exposed.