Unfortunately, like most sites HN has its fair share of borderline-psychotic oddballs who like to send angry e-mails to people and attempt to upset them.
I've had a few private e-mails responding to innocuous comments of mine over the years threatening all sorts of stuff. I put it down to the "if you're out there enough, you'll keep encountering that 1% of crazies" rule and assume my reach must be getting better ;-)
More interestingly, I once had a slightly heated debate on HN - nothing serious - just different points of views - and in the end the person managed to hunt down my email address just to apologize in case there were any hard feelings (which there weren't). This community is one of a kind, even with your occasional borderline-psychotic oddballs :)
I've had a few private e-mails responding to innocuous comments of mine over the years threatening all sorts of stuff. I put it down to the "if you're out there enough, you'll keep encountering that 1% of crazies" rule and assume my reach must be getting better ;-)