I particularly like this example, which the author acknowledges is extreme:

"3. Be positive.

"This can really be hard when smart people debate, but try it anyway. Notice the difference between:

"Person A: Water is dry.

"Person B: No it's not. You're full of shit.

"and

"Person C: Water is dry.

"Person D: Not in my experience. What data have you encountered to cause you to arrive at that conclusion?"

I really like those "what data have you encountered" questions. In a lot of threads, I silently upvote replies that ask people making striking, unusual, bold, or implausible claims to please provide more information. (Too many of those helpful questions, alas, never get answers. But I'll keep on upvoting follow-up questions looking for facts when I see them.)

The author finishes his list of good suggestions with

"10. No list is ever exhaustive, on Hacker News or anywhere else. Anyone have any more suggestions?"

I'd be delighted to hear other suggestions about constructive participation on Hacker News too.