Re 7354815, what we did was reopen the thread past the editing window so a concerned user could post relevant new information—that a controversy involving his company had been settled. That was only fair, and we'd do the same for anyone. I've done similar things a couple times for other HN users who wrote in to ask, and will continue to, because I'd feel bad not to. It has nothing to do with YC.
That was a unique case in my memory. "Often rank a pro-YC comment to the top of a thread" is pure fabrication. As I've explained many times, we intervene less, not more, when stories are anti-YC, precisely because of the conflict of interest. It's literally the first thing PG emphasized to me when explaining how to moderate HN.
A recent example is https://news.ycombinator.com/item?id=9622711. That class of outrage thread is something we routinely penalize, but we penalized this one less because it was about Airbnb. There's no way it would have stayed on the front page for hours otherwise.