[Don Pensack]

OK,
I talked with an expert in optical design, and he explained coma to me as a paraboloidal aberration and explained why there was so much confusion. The explanation was really quite simple.
The linear size of a comatic image on the focal plane of any scope is dependent on distance from the center of the field.
How it relates to focal length and focal ratio is as follows:
A 10" f/4 exhibits X coma at the edge of a 40mm field of view
A 20" f/4 exhibits .5X coma at the edge of a 40mm field of view, yet, because the magnification is double, the linear size of the comatic image at the edge of the field of view is exactly the same.
This is why the linear size of a comatic image appears the same at all focal lengths of identical f/ratios at the edge of the same sized field of view, and why a coma corrector can be designed to work with a set f/ratio in mind.
At the same time, the linear size of the comatic star image on the focal plane of the scope, at the same distance from center, will be less with a longer focal length, and it is here that describing coma as lessening with focal length is correct.
A coma corrector that is designed for visual use will take magnification into account, so would be designed to correct for f/ratios.
A coma corrector designed for prime focus photography will be designed for the size of the photographic plane and the focal length of the scope.

Where the confusion lies is that they are one and the same. It depends on your point of view as to which explanation makes the most sense. FOR IDENTICAL FIELDS OF VIEW, THE LINEAR SIZE OF COMA WILL BE IDENTICAL FOR ALL FOCAL LENGTHS OF A PARTICULAR F/RATIO.

So, the linear size of the comatic star image IS made larger by magnification. He had no explanation of why I (and others) see lessened coma at higher powers. I, since (on another forum), have run into some individuals who see the same coma in the field at all magnifications, so it might be a psychological phenomenon on my part.