Hey, not sure whether this actually helps but apparently we've missed something. According to Steven Moffat, "I've been online and looked at all the theories," Moffat told the Radio Times. "And there's one clue that everyone's missed."
He added: "It's something that Sherlock did that was very out of character, but which nobody has picked up on."
(my source: http://www.digitalspy.co.uk/tv/s129/sherlock/news/a360733/steven-moffat-sherlock-fans-have-missed-big-clue.html)