It sure beats the Reddit system where you think you are interacting with people, only to find out a couple of days later that your fresh account is shadow-banned and nobody is seeing your comments and that none of your likes went through.
I wasn't aware HN had it, but considering the number of [flagged] by people who work for big tech I'm sure some people actually posting truthful things have ended up on the shadowban list
"Spamming", or rather, responding too quickly in an intense discussion, is cause for automatic shadowban here on HN. It happened to me on a previous account some years ago. The posts themselves were harmless, I merely responded to too many users in a too short timeframe. My attempts at having the ban undone also turned out to be a waste of time. Completely absurd.
At least Facebook tells you that you are banned.