[metellus]

Not in the guidelines, but it is kind of addressed here: https://news.ycombinator.com/newswelcome.html

Specifically: The most important principle on HN, though, is to make thoughtful comments. Thoughtful in both senses: civil and substantial.

The test for substance is a lot like it is for links. Does your comment teach us anything? There are two ways to do that: by pointing out some consideration that hadn't previously been mentioned, and by giving more information about the topic, perhaps from personal experience. Whereas comments like "LOL!" or worse still, "That's retarded!" teach us nothing.