I have some evidence that might sway you: there have been many threads on here that are critical of YC backed companies, sometimes pretty pointy ones.
For those threads flagging is turned off not on. So YC companies actually have it harder on HN than non-YC companies very specifically to avoid the accusation of bias.
I've also seen people associated with YC backed companies here downvoted into the toilet for spouting unpopular opinions. The only thing that possibly could happen (and that would be fairly hard to detect) is brigading on a company level, but I would accuse the likes of Google and Apple of that long before I would do so with the YC mods. Think about the opportunity cost of moderating this site. If you take that into account and then combine what you know of Dan and Tom with them selling out their integrity for a pittance if it would come to light that they did so it would wreck their reputation, which is pretty much the only compensation they really get here.
So I'm not buying it and I'm more skeptical of YC than most on here.
There is zero evidence that would sway me other than full transparency into all company records, which I recognize as an implausible ask.
I do not trust companies, or any organization involved in their creation and investment like this forum, to speak honestly and openly.
They have an incentive not to and their peers have proven time and time again that this incentive is too enticing to avoid.
I have seen and taken part in threads on here that were negative for ycombinator and/or their business partners be removed at almost machine level speed.
Maybe it’s the company, maybe it’s the community opinion, maybe it’s another option that I didn’t anticipate.
Regardless I assume it’s the company because they have not proven otherwise and companies in the American business setting are guilty until proven innocent to me.