I have wondered about that myself...(God, I hope it's not me is it your talking about?)......perhaps they do it that way as they might be busy people and dont have time to comment individually on everyones work. I guess in a way at least you know they have seen something you have posted that has caught their eye in the first place worthy of a comment. I am busy too sometimes and my comments are short and abrupt but i do enjoy seeing what I comment on....
cheers sue