HUGE SPOILERS FOR SHERLOCK 2X1: A SCANDAL IN BELGRAVIA
Even if you don't care about the spoilers, you won't understand it if you haven't seen the episode.
Yes, it is meant to be a little humorous.
No, I don't own the show, that's the BBC and the BRILLIANT Mr. Moffat.
Dramatic Irony
John woke to the sound of the shower running downstairs. He rolled over, discovering that sometime in his sleep he had managed to twist the coverings around him to the point where it made this act very difficult. He hadn't slept well, and he knew why. It had been four days since Mycroft's visit, and to be honest, John really wasn't so sure where he stood. On one hand he wanted with all his heart to believe that Sherlock bought the lie that Adler was in the US. Another, more rational part of him perhaps, knew that Sherlock would have read it in his eyes and hair and left pinky-finger what had really happened. Not just that she was dead, but that she'd been beheaded by terrorists.
Sherlock wasn't really one for self-deception, so if he had noticed then it was for John's sake that he hadn't said anything, and that was infuriating enough. Was the detective, in his grief, trying to coax the profession from John's mouth? That seemed very Sherlock; if not any more comforting, or at the least any less annoying.
The more John thought about it, the more he realized it could only have been Irene Adler who could have pulled her death off so cleanly, leaving only him as a loose end with a responsibility to never let Sherlock know. When she had "died" the first time, Sherlock had spent six months in utter self-neglect. But it hadn't been grief, or love or any fathomable human expression of emotion. It had been fascination. She was a puzzle, an enigma personified by the passcode on her phone and he was a detective with a bitter compulsion to solve the case. That was enough.
As far as John could tell, this time there had been no behavioral change that signified mourning. It could have been that he had gotten it all out last time, and now couldn't be bothered to muster that kind of energy that mourning her over again would take. But for Sherlock that didn't mean anything. It was three am and he was taking a shower, and John was beginning to note that there was nothing abnormal about this. That was okay, that was how Sherlock worked. He did things that made no sense to outsiders and that took eighty times the energy than was necessary on a regular basis with no thought of doing things differently. It was how he dealt with life; at least when he chose to acknowledge it. He composed violin music and deprived himself of sleep and calories for days on end. He drove his body right up and over the edge and then demanded still more from it. But as bad as it was, and as much as John hated to admit it, there were less healthy things the man could be doing to himself.
As for Irene, though, the whole situation was clearly affecting John more than Sherlock at the moment. He'd thought, when Sherlock had taken the phone, when he'd expressed sentiment; that he was in for another six months of withdrawn, sad violin music and listening half-heartedly as Sherlock's starved mind worked out a hundred plausible ways she could have survived. But that wasn't what he was doing and that had John worried. Sherlock hadn't noticed or he didn't care; the former virtually impossible, and the latter just as unlikely. It was a painful game, to be sure, and he, like the good friend he was, would keep it up for as long as it took. He would let the ruse continue until Sherlock inevitably figured it out or admitted to knowing what had happened from the beginning, and if he never did that was okay too.
Because a little dramatic irony now and again might be difficult, but sometime it just had to be endured for the sake of all involved.