Yes, headrests are supposed to be down for takeoff and landing. It is required so that a flight attendant will have an unobstructed view through the cabin in an emergency. (Yes, really, this is the reason). Sometimes if landing is imminent, there isn't much time to be too terribly gentle with lowering them. I know they are uncomfortable ... I am only 5'6" and they bother me too. As far as some people being asked to lower them and others not ... I think the really high headrests get attention and those up maybe only an inch are overlooked. In any case, unless it is a long taxi, the moments of discomfort are not long. If you put them down when requested, then we won't come by and lower them for you.