Great points. I also see it as an assertion of the patriarchal power dynamic. You would never walk up to a handsome male stranger on the street and say "you're looking good today." Or if you did, you would not be surprised if he ignored you or told you rudely to get out of his way. Because people with less power don't approach powerful people in public spaces. Only the other way around. To tell a random woman she looks good is to tell her she's beneath you. You have the power to comment on her appearance whenever you wish, whether she wants you to or not. It's rude at best, and like you point out, threatening and dangerous at worst. Obviously, the rules change depending on the venue. If the woman is standing at a bar in a club, she might welcome a compliment from a stranger. But not if she's walking down a public street.