Thanks, Daniel, but I think I've checked every item in the Comments config panels, including Security, which is set to far greater length than is being displayed. I find the "Layout" settings descriptions quite unclear, but have tried various permutations of Layout settings, none of which affected the displayed comments in a visible way, nor made visible the expected "read more" link. So, it's probably accurate to say that the Layout parameters are not being enacted.
FWIW, I DO receive an email of the full post, whose latter portion is not visible online.