Thanks for your answer.
From the guidelines, I see: "If you think something is spam or offtopic, flag it by going to its page and clicking on the "flag" link. (Not all users will see this; there is a karma threshold.)". Fine, I have no issue with a Karma implementation.
But, I don't think my article was about spamming. I was just announcing the new release of JXTA/JXSE 2.6, an open source P2P project initiated by Sun Microsystems in 2001. This is not different than PostGre announcing a new release (for example). I don't see why it would attract 'negative' Karma.
My issue is that I don't see the flag link. Moreover, there is nothing telling me if I have attracted 'negative karma' at all. If people 'vote' that way, I believe they should assume it and this information should be displayed (if not to inform the poster of spamming).
After all, HN is about providing opinion about posts. I don't see why negatives should not be revealed and accounted for publicly.
Conversely, I can imagine people instrumentalize this 'flag' link to kill a post not in their interest. Far fetched, but possible. There is a gap to 'get away with murder'.
I believe more transparency about negative karma would not hurt HK overall, and would improve overall experience of newcomers.