I don’t want to invalidate people’s experiences with this, but as an attractive woman who frequently gets complimented by people in public (women and men) I have to say I almost NEVER feel uncomfortable about it. I also compliment people I think look good all the time. Strangers in the street, on public transport etc. And it IS just a compliment. And you know what? It 99% of times makes their day. The other 1% of times they just seem surprised you noticed and maybe feel slightly awkward.
I think the key is to compliment people on things that they chose for themselves. Rather than on inherent physical characteristics that are just due to genetics. So complimenting someone’s haircut, style, hair colour, hat, unusual fashion choices etc = good. In fact I go out of my way to compliment “alternative” fashion, even if I’m not a massive fan of it for myself. Like a goth/punk/Lolita/quirky old lady/people with neon hair etc.
Complimenting someone’s body shape, facial structure, eyes, breasts etc = creepy.
That’s probably why I don’t feel uncomfortable when people comment on me in public. Because I wear unusual clothing that’s very colourful, and flower crowns I make myself. So I KNOW when people compliment me it’s not because of my body, it’s because my style makes them smile. And that was the intent of the style.
If someone said “hey nice boobs” to me in the street that would be creepy. But an old lady saying “you look gorgeous”, a young woman saying “I love your dress” or a man saying “you look like something from a Midsummer Night’s Dream”? That’s ok.