I've definitely seen it happen, so saying that it isn't true is not very honest. For instance, I distinctly recall a post a year or so ago where someone complained about a YC company that had ripped them off, and PG replied saying he was killing the thread and quoting the penultimate paragraph of "In submissions" from posting guidelines (https://news.ycombinator.com/newsguidelines.html).

Maybe you don't enforce it as hardly as you used to, or maybe this thing I saw was a one off, or maybe that guy at the time had crossed a starker line; regardless, saying that it isn't true is misleading.

First, you said "typically". That's pretty strong.

Second, I know from experience how distorted people's interpretations of these situations can be. You seem sure that you judged one example correctly; I think it's more likely that you jumped to a conclusion.

The first thing PG said when teaching me how to moderate HN two years ago was: whatever you do, don't censor stories because they're anti-YC. I think about this every day and try to stick to it. But that doesn't mean that posts like the OP get a free pass just because they say bad things about a YC-funded startup. If we applied the rule that mechanically, we would fail our primary responsibility, which is to keep the quality of HN high. So we do what we can to balance the concerns.