I think it's an irritant trait we Koreans have. We will comment about others' looks non-nonchalantly. It's may be just small talk besides just pointing out flaws or compliment. Even thou I don't like this trait, I get myself commenting about a fellow Korean's looks as well. It's just normal.
I usually avoid making such comments to non-Koreans as it may look weird or rude. I guess when in Korea, they may just forget/not know about this behavior not being common for outsiders, so they will just comment as usual.
About complimenting foreigners despite not fitting Korean beauty standard, they aren't being judged on these standards of course. I can't say for myself, but I imagine most mean it. If someone is overweight or big headed (this is a thing too), we would bluntly comment on that too.
That makes sense. Thanks for responding! Is there a reason why foreigners are not judged on the standard?