This is beautifully written, and I love so many things about it that I can't pick just one (but if I did, it probably would be how right it sounds and how right they sound). It's a gorgeous but also a very very painful story. I have to tell you that this line...

“When did ‘I’ll tell him tomorrow’ turn into weeks and months and years until suddenly all your tomorrows were used up?”

...had me welling up at my desk and hoping nobody would notice. And also hoping that Jack would take Sherlock along to find the Doctor and that Sherlock would find a way to rewrite history so that John would still be with him.

Thanks for sharing this!