One liners including 'jokes' aren't really appreciated on HN. HN is not reddit, and has a different ethos. Some people do manage this occasionally, but in general if you make smart aleck one liner comments, usually you'll be downvoted into oblivion.
I'm not complaining, I really wanted to know what I did wrong. I was a bit worried that the reason for downvote was the content; as it turns out it was the form, which is perfectly understandable and I have no complaints about it whatsoever.
If you look at my comments you'll see that I don't use this form very often - or maybe even at all. I had slightly worse day yesterday and that's the result and I'm sorry. Do you think I should delete this and the three more comments in this thread, which were made in similar manner?
"Do you think I should delete this and the three more comments in this thread, which were made in similar manner?"
No (imo). Obsessing about 'correct form' and karma is just as bad as completely ignoring it. Everyone gets downvoted once in a while. Learn from your mistakes, and go with the community ethos, and you'll be fine. Karma is just a number on a webpage.
I didn't even think about karma, honestly, I asked having in mind the quality of the thread. I'm still rather new here, I started posting just a couple of months ago and learned by watching others and not from a textbook of rigid rules and that's why I'm still sometimes unsure about how to proceed; even more so because I actually do care about the 'ethos' (although I probably wouldn't use this word) more than about points of any kind.
Either way, thanks for advice and for taking the time to respond even though this was probably one of the least exciting topics you could discuss here, I appreciate it very much.
And yes, don't complain about being downvoted. From the HN guidelines, http://ycombinator.com/newsguidelines.html
"Resist complaining about being downmodded. It never does any good, and it makes boring reading. "