Well I think I understand what the hint is that "everybody missed": it's Sherlock saying: "It's a trick, a magic trick". Well, what about that then. Isn't that a big hint? Let me try to explain: there are a lot of magic tricks using mirrors. Mirrors making things disappear. We all see that there is a platform beneath the ledge Sherlock is standing on. And he doen't jump: no he falls of. Which would just make him fall on to the platform below. And he tells John to focus on him while he's falling. So John can be the witness of him actually plunging to his death. Just to be certain that John is an eyewitness to the suicide. Otherwise it would leave room for speculation. But what if it was a body from the morgue falling? And Molly works in a morgue right? I guess it would be to hard to arrange for a body to looking like Sherlock. But a mask and wig maybe? Make up used in a morgue? Does leave something unsolved though: Sherlock obviously moves while falling. I really have no explanation for that. But maybe somebody else can try to work that out? Really want to watch the next series to see if anything at all mentionned by all of you was correct. I like the injection idea, as it has some interesting proof from the episode. But I still like my theory as well.
The show is a great favourite of mine, and I'm a big Dutch fan, but love to ponder on this. Great stuff!