Like you, I have always found Mark Prior's outstanding accomplishments in baseball to be compelling and highly notable.
His serious injury history is very troubling, of course, and the results of his injuries were devastating...especially for him personally, I'm quite sure.
Beyond that, it is extremely frustrating to plumb the depths of naive (or sometimes worse: con-like) opportunism that such cases seem to create for some people on the internet. I personally believe that if the medical people, trainers, and biomechanics experts who were/are close to Mark Prior were able to provide reasonably informed explanations that would help others rationally avoid MP's career-ending history of problems....they would provide it.
But, Monday-morning quarterbacks abound on the internet and they will have their say, no matter what...