Anything the AME knows, he is obliged to report to the FAA. I think your personal doctor should not be your AME.
I absolutely agree about avoiding an AME as a personal physician. I think your first sentence answered the first part of my question which was actually about using an AME as a pre-exam consultant to "clear" certain issues before making a new medical certificate application.
I'm still wondering whether there is any
written guidance on an AME's obligation to report anything he or she learns about a pilot outside the course of the formal aviation medical examination. There are a number of these issues that may be of interest. For example, this forum isn't anonymous. What if an identified pilot, though a question, discloses something about him or her self that is a cause for disqualification; are you obligated to report it? Written guidance tends to clarify questions like that.