I am running tech site with 10k users on which i made surveys about politics with possibility to comment by users. I've stopped because there were so many conflicts, such bad emotions, then users moved their personal conflicts to other discussions on forum. After stopping the political surveys everything is a lot more stable and people are nicer to each other, without any biases, they discuss about software, hardware etc.
This was very good decision, will it work for HN? Probably yes, it worked for us.