1. Be respectful.
2. Stay on topic.
3. Move the conversation forward. This sounds like a repetition of #2 but there is often a distinction in that, say, a discussion about a new product feature is likely not the time to discuss the company’s history with features. Going in that direction is moving the conversation sideways.
4. Provide supporting evidence for what is said. Claiming something like, “I’d never buy this from Company X” is a baseless statement compared to “I’d never buy this from Company X because A, B, and C are an indication I won’t get much support beyond the 90-day warranty and that’s not enough at that price point.” The trick I use for this is to include a word like because since it compels an explanation.
5. Avoid attempts at humor. For one, text mediums like HN can easily lead to misinterpretations; there are many people reading for whom English is a second language, so being clever can cause confusion for those readers; if my humor were so good to be worthwhile for the amount of readers a place like HN has then I should be a comedian. I'm not a comedian.