Seems highly unlikely given the the number of posts if such a threshold is fairly applied, don't you think? Obviously this is a policy that has direct ramifications on the business interests of the founders of YCombinator. They probably ought to be careful if they really are interfering in moderating.
From what I've observed, there's no conspiracy going on here. The mods are very open about the actions they take, and in the case of YC-related topics, have removed automatically applied weights and user-flagged actions to ensure they are discussed, even while flame wars rage on.
Human psychology being what it is, we pay attention to what happens to topics that interest us, in particular if it's negative. This gives us a biased view. I think if you were to do a study of submissions on HN, it wouldn't likely support a view that the mods or the HN algorithms are doing anything untoward. (I'd personally be interested in seeing such a report regardless of the results.)
I think I may have been unclear when I mentioned the number of comments with respect to triggering the overheated discussion detector: I think its based on comment rate rather than absolute number. (The exact rules of the site aren't open.) Yesterday a post was sitting at number 1, with a comparable number of votes to the one in the number 2 slot. As the number of comments skyrocketed (over a hundred in a couple of hours), it plummeted in rank even as it continued to be upvoted. And the topic had nothing to do with YC or even business, for that matter.
There is one other behavior that may be at play. User flags will affect ranking even prior to the '[flagged]' tag appearing. This could also be the case for either of these submissions.
Also, please be aware that flagging is nearly always a result user flags, not interference by the mods. Likewise, the algorithmic actions are automatic, not reviewed and applied by mods on a case by case basis. I've seen reference to the mods adding weight to a post, but this I believe is few and far between. I haven't seen this mention in months. And from a practical standpoint, the mods are just two guys. They do their best in tending to the forums, but they're not watching the site 24/7. They're not reviewing every submission.
