If someone cat calls me I'm flattered and just give them a cheeky smile, or pretend I didn't notice because I don't want to assume they're talking to me. I think the only time I'd probably genuinely feel uncomfortable is if I was walking home alone at night or if it was a seemingly creepy guy. But generally during the day it's pretty harmless and it puts a spring in my step to be honest. Do girls actually feel uncomfortable when it's just a builder or a random guy on the street in the daytime? Is it fine if the person is good looking?
Same with messages online, I'll always just take it as a compliment.
I quite like that guys go out of their way to compliment. Girls don't do it to guys as much. I personally can't imagine having the balls to cat call a guy but I don't think it would be a horrible thing to do. I'll admit some comments are nicer to receive than others but they're all still pretty great to hear deep down. I know some people see it as intimidation but I don't really. In that moment I don't feel any lower than them, quite the opposite. I suppose the only time it feels a bit awkward if it's in a really public place like on the train where everyone can see the interaction. But even then it's not a big deal.
Obviously if someone said something like 'nice flaps' I wouldn't take it as an amazing compliment but I'd find it quite funny.