I've noticed that a common tendency on HN to avoid downvoted is to start your comment by saying something like 'time to spend some karma'. It seems surprisingly effective, I think because many on HN want to think they're contrarian so expressing that your opinion is contrarian is a way to garner support.
This almost certainly isn't true, it's far more likely you've only noticed it when it worked. Every other time, when it didn't, the comments were buried at the bottom of the article.
