There are many possibilities, but I have no idea what happened here: Troll farms and astroturfing could have an effect, but I don't know who would be motivated

There are many possibilities, but I have no idea what happened here: Troll farms and astroturfing could have an effect, but I don't know who would be motivated to act on this thread. I doubt the Russians care, though simply creating dissension is part of their (and others') strategy. The white supremacist movement certainly would oppose white people supporting PR, and they are active on HN. Again, I have no idea. My point is, there is much more than bots out there. HN needs to find a solution; what it does now isn't working well enough and IMHO empowers the trolls. That's not a criticism; nobody has solved it yet but HN is the right place to take on the big problem and solve it.