there are ways to know it, especially for comments of people that is not related to you at all (like that website), there is no interest in them in make you happy saying you're pretty or in make you sad saying you're ugly...
but.. I must say for getting a boyfriend this is not very important... I know many pretty celebrities who thought they were ugly cause no guy aproached them in high school, and it was quite the oppossite, no-one was brave enough... Sometimes beauty backfires to the person. Though maybe this only happens when you're "very" pretty and maybe it's only a problem too if you're "very" ugly. U know this society is made for "averages", a too short or too tall people have a lot of problems.
More ways to know... if you walk through a street and some guys (never a single guy only) pass your way to you... let them see you... and then...
... after some seconds... turn around so you can walk behind them and eventually pass them (It happened to me casually... not that I do this...
).
Maybe they will be talking about you, especially if you are very pretty or very ugly, so if you want the red pill, here it is.