A few years back I went to a training chiropodists (since it was cheaper, and local) to have some problem looked at/manipulated/whatever. Roomful of students, me in my underwear. Not one of them nor any teacher felt it polite to mention that the hat I'd worn there had somehow reacted with something; maybe the rain, maybe me, and left a massive black mark across my forehead. I only became aware of it afterwards, when I looked in the mirror after dressing again. One would have thought someone would have had the decency to point out the mark so I could remove it, but no, apparently.