Over the years, HN has definitely seen an increase in idealogical group activity (low quality comments and voting/flagging), but I'm not inclined to believe dang and tomhow are putting their thumbs on the scale. HN remains a gem from the community moderation and the mod's largely hands off approach.
YC on the other hand has become a red flag for me. I agree with the critique of the companies they are funding, and would add that they tried to scale things that don't scale - enlarging class size and mentor load (like our public education system) - and it has had the same outcomes.