How high the comment quality here usually is becomes really noticeable when it's lacking under a post. The most common offenders are political posts with outrage potential, especially while knee-jerk responses are flooding in and before measured comments have had time to rise to the top.
Recent example was https://news.ycombinator.com/item?id=33931384 about cash limits - Sooo many comments are just "Tyranny!", "EU bad!" and overall unmitigated cynicism.