With all this talk about the jacket, why no talk about the hole in the jacket collar?
The jacket and shirt collars were above the entry wound at the base of the back of the neck. The base of the front of the neck is basically where the bottom of the necktie knot is; the base of the back of the neck then (projecting backwards horizontally) is an inch or so above the base of the front of the neck. Obviously the collars and, in the case of the jacket, the bunch that's behind and to the right of the midline of the jacket collar, are above the base of the back of the neck.
The bullet entered below all that and through where the jacket and shirt had single layers of clothing.
If we're seeing a lot of clothing on the top-right-back of the neck area, and the top of it is substantially above the neck tie knot in front, we're looking at a jacket bunch. In the Zapruder film, the right side of the top of the President's jacket is both higher than the left side and is substantially higher than the level of the necktie knot.
That can only mean there is a bunch (above the area of the entry wound) that is displacing clothing.