I accidentally get one particular cardigan inside out so often that I am almost afraid to wear it, and even when I wear things the right way out I have a very bed habit of having labels sticking out.
I give one-to-one lessons, and have lost count of the number of times I've only discovered my mistake hours after a lesson.
On one occasion, I discovered that I had been teaching with a clothes peg hanging from my cardigan. On another, I found that I must have given a lesson with blood all over my face, from a nose bleed earlier in the day.
Not one single time has a student (mostly adults) ever said a single word to me!!!
But would I say something to someone else in a similar situation? I honestly don't know. It would depend on the person, I think. When I was younger, I would definitely have kept quiet, but I am becoming far less reserved with age so might speak out!