Someone just pointed out a nice Twitter post about me! When I didn’t like teachers in high school, I just whispered in the hallways about it!
Edit: I agree with summerinphilly, it does tell me a lot about the student as opposed to anything about my own teaching!
People who don’t have the savvy to know nothing is private online will suffer in real life. I always mention to students if I find out in a public way even if I am not the teacher involved. There is a way to handle it but I think up front is best.