Just a quick post this, but after rewatching it I think I’ve figured this “how did Sherlock do it?” thing.
When Sherlock first looks over the edge and asks “for a moment by myself”, there’s a bus parked alongside the hospital. After a minute or so, and next time we look down, there’s a lorry full of bin bags there. He was obviously stalling.
Also, he wanted Watson to stand in a specific place where he knew that he could see him on the roof, but not on the ground, as he directed him exactly to the spot where he was standing and told him to “keep your eyes on me” (probably so he didn’t see the bait and switch that I’m about to talk about).
Now, look at when he jumps. WAY too far from the building considering where he is supposed to have landed (also, jumping forwards, despite the body being side on), and as we pan to the body, the lorry is driving away, I suspect with his body in it.
So, who is on the ground then? Well, his double. His double being the guy that Moriarty used to kidnap the children, hence the being scared of his face despite “never meeting him before”. I’m assuming a double as opposed to a mask at this point, as I expect a mask to be too loose of a plot line. That said, in the last episode, “The Hounds of Baskerville”, whilst in the Baskerville facility, “human cloning” was mentioned. Could be a bit tenuous, but you never know.
He went to Molly just before the end so that he could ask her a favour so that she could perform the autopsy and “verify” his death, even though it didn’t occur.
That’s what I think anyway.
UPDATE: Also, I just realised that he was being buried in a Churchyard at the end. You can’t bury suicides in a Churchyard.