As I stated, you'll still find low quality content and comments on HN with name calling and terrible takes when a thread is slightly political. It's not a platform issue. It's a popularity and subject issue.
Allow 10 friends to talk about flowers and it will go great. Invite 1 million strangers to talk about politics and it will degrade within minutes. The issue there isn't solved through subjective moderation.
No you don't as HN clearly shows.
There are plenty of examples where when you have active moderation and the site sets the tone for discourse the quality of the discussions improves.