I've noticed that too, (not so much here, though, as elsewhere).
I think, with the internet, true emotion is hard to express. So people may come off as rude even if that's not what their intention was just because of the fact that you can't see them express what they are trying to say, you just read their words and interpret it (and one may interpret it differently from another).
Thank goodness for emoticons; they help with that a bit.
I think, though, you can definitely tell when someone really meant to be rude. Like, they attack the person that made the comment instead of simply correcting them or offering their own opinion. You see this a lot on sites like youtube; people call others names and such (that's what I mean by attacking).
No one likes to have their feelings hurt, and calling people names online is a form of cyberbullying, which is
not accepted here, nor on many other sites. But when people are simply correcting another person, and even if it comes off as "cold", simply remember that they probably did not mean for it to be interpreted that way (like said above).
Most are not trying to hurt feelings when they're expressing their own opinions or additions/corrections.