Since this re-appeared in What They Died For, I have not seen the cut on Jack's neck discussed anywhere, but it has to be hugely significant.
So, on this basis, I propose a small theory, for which I have completely no evidence whatsoever, but which seems to tie together a couple of distinct loose ends, and which if correct, would "prove" that the writers had some sort of plan to connect the beginning and end of the show.
Theory: Jack almost chokes to death in the OT, and someone attempts to save his life by performing an emergency tracheostomy.
- In Pilot, Part 1, Jack asks Boone to find a pen in order to perform an emergency airway for Rose.
- In LA X, Parts 1 & 2, Jack again asks for a pen in order to do the same for Charlie.
In neither case was it ultimately necessary, and the procedure was never carried out; however, if such a procedure was performed on Jack in the OT, it may have been so traumatic that in the FST he is experiencing a literal 'bleedthrough'.
Note: Most emergency tracheostomies are executed at the front, underneath the Adam's Apple, rather, than from the side; however, it does appear that there are occasions when an entry from the side is possible.
OK that's my two penneth.
It's probably total nonsense, but has anyone any ideas which might be correct?