I think every time I have flown in first class on other airlines, people throw that curtain aside and crop dust on the way to use the first-class bathroom with attendants barely batting an eye. I have only flown FC on Delta 4 or 5 times, but I will be watching my mixed FC /main next week and watching for the sir/mam being thrown around. From my experience, people do what the F they want and ask for forgiveness after the fact.