I don't think moss is the problem, Elaine, and with your experience, it certainly should not be. Don't forget I deal with several hundred people a year. I would guess 20% have experience growing orchids, the other 80%............well, you can guess. Each and every one of those 80% have grown houseplants, for better or for worse, and when they see the potting soil the least bit dry, water, baby, water. Orchid media pretty much always looks dry, even sphagnum moss, so guess what they want to do? Using moss, where over-watering is a problem, is a killer. At least that's my experience and opinion. My opinions are worth what you pay for them.
I would think that anyone who successfully grows epiphytic orchids in potting soil (and I think we can all agree that this is just not the thing to do), has to have an open potting mix AND carefully controls watering. Shoot, if I don't open up my potting mix with lots of orchid media elements, I can't even get terrestrial orchids to do well. Ask me how I know!