I don't buy that argument - why aren't many of the other short comments in this page getting the same treatment when they're not adding to the discussion either?
I've seen this elsewhere - if someone says they're being sarcastic, they're downmodded to hell... but people in the same thread saying the same thing in the same sarcastic manner, but without the admission, are left alone.
I find this inconsistency annoying - it appears that downmod-friendly HNers are more interested in making a pretense to politeness than actually moderating content. It only takes a single dissenter and your words are already diminished on the page.