Mosch (who apparently follows the links I post more assiduously than I do) directed me to this page by a doctor who thinks the problem with hearing people eat is a form of hyperacusis. It was interesting and does fit my experiences. Mostly it made me feel grateful that (a) my experience is so mild compared to some people's, and (b) this didn't start when I was a kid.
I really don't mean to post about this like it's a big disorder or something I'm stricken with. It is only a very tiny part of my experience of life.