Earlier quoted context omitted.
They're entirely forthcoming about this: except for job and launch posts, YC posts aren't ranked differently, and YC company upvotes are treated no differently than anyone else's. I think it'd be hard to count how often Dan has said this. You can choose, of course, not to believe him about this (I have a hard time thinking of a person in this industry I trust more than Dan), but you can't ask him to be more forthcomi…
Sure, I also, still, feel some of the kinetics need to be explained to avoid confusion. Like the homepage doesnt make much sense to me after all these years of reading HN. As I write this there are 160 upvotes in one hour on this post and it is still #9, with many weaker posts ahead of it.
The specific answer (about this post) is that moderators haven't touched it in any way. Twitter.com links have a mild downweight, along with many other domains that produce a lot of sensational/offtopic content (relative to HN). That includes nearly all major media, forums like reddit, etc. Other than that, all you're seeing is the regular HN algorithm at work. It's more complex than just points + time—we've tweaked it over the years to (try to) do a better job of selecting for intellectual curiosity, dampening flamewars, and so on.