I find the most common trap on HN is pedantry. Generally, I see a lot of thoughtful ideas but the discussion tends to focus on minutiae instead of the core idea.

Although it's generally very civilized and might be higher than an average in internet, I can't say it's high anything except computing. In every other topic there are mostly "I read some articles in internet and now I will share my knowledge" people. Many people have said it and I can confirm it regarding these very few topics I feel competent enough to comment about. If not anything else, then LK-99 discussion made it very clear.