I think it's the general texture of the "LOL", smiley emoticon, and exclamation more than the gratitude. A comment that doesn't add much, and looks like it was made quickly often produces bad results here.

Maybe it's because people are scared of losing the fantastic signal:noise ratio that's a hallmark of Hacker News and is very hard to find in internet discussion. The parent comment looked like more general internet discussion, but if he'd written, "This is exactly what I needed to hear in plain English: I keep meaning to code up this simple timezone app but I've been scared to execute it. Wow, that was valuable" - well, that probably would've been quite high in the positives.

Oh, my:) You know, I appreciate your help for pointing and explaining me the down-votes. There is one thing I want to say though: If this Karma thing is important for you guys, just do what you think is best. As for me, I don't care if my Karma here is like -xxx or +xxx, alright? I registered here for more important purpose, like getting to know good people and read good news I missed in my Google Reader. I don't troll here, so if I feel like saying a thank you to one of you, I will do so. As I said before, do what you think is best. Cheers!;)