I was out with a couple hearing aid users this weekend. Both are high level engineers/scientists with inquisitive minds. They were on board with me. From all of our understandings, the ear has different parts responsible for hearing different frequencies. Areas that are damaged result in reduced hearing at those frequencies. Hearing aids boost the frequencies in the diminished areas. They've never been told that a hearing aid would hurt what they have left. And sure, I could make a mistake, and over-do a frequency range, and as a result, damage my hearing in those frequencies. But so can an audiologist. They would be working off the same hearing test results I would be working off of.