Sorry to ruin a good spy story but no one at YC is "gleaning" such information from HN, other than as casual readers looking at the same stuff everyone else sees.
Also sorry, but there are no hidden reasons. Here's why: we don't do things that aren't defensible to the community in the first place. That way when questions come up, we can answer them publicly in good conscience. Maybe the answers won't convince you (though we can dream!) but I believe that the bulk of the community does find them convincing, because if they didn't we'd never hear the end of it. Occasionally we screw up and do something that the community strongly dislikes, but in that case the solution is clear: say sorry and stop doing it.
The voting ring detector prevents abuses like people upvoting their own or friends' posts. Shadowbanning is mostly for new accounts that show signs of being spammers or trolls; if an account has an established history, we say that we're banning it and explain why. I don't know what "blacklist names on articles" means but anything like that would have an easily explainable reason too.
There's plenty of transparency in the sense that there's no question people can't get an answer to if they simply ask. https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que... We answer such questions every day, just like I'm doing here, though you didn't ask.
Sinister terms like "market manipulation", "collusion", "control the narrative" are impossible to answer because they don't mean anything specific. If you or anyone were to spell out exactly what you mean by them, it would be easy to clarify what we do and don't do, and why.
YC founders don't collaborate as a bloc on HN and the same anti-voting-ring and other anti-abuse measures apply to them as to all users. pg added the orange usernames in the early days of HN and YC, as a way to help the early YC community get to know each other. It's a perk, for sure, but more a kind of flair than some sort of secret power.
Have I missed anything?