It's not a perfect system. IMHO, HN could use some meta moderation. I get the occasional down vote. Just the price of having opininos and expressing them. It's actually quite common for me to see the same comment recover afterwards and end up with a positive score. To me that signals that HN has some bad actors abusing their moderation rights to down vote anything that conflicts with their world views.

Meta moderation could deal with these users more effectively. Take points from their precious reputation and ultimately take away their moderation rights in case of repeat offenders.