Hacker News is aggressively moderated, it's very much "quality over freedom" as far as speech goes. I don't know why people keep expecting it to be like 4chan, just because it has "hacker" in the title.
One thing is flagging (just like this), another thing is showing a different version of the site based on the user, the latter is scammy and is meant to give users the felling that their post is there (while it's not) but no one is looking at it.
Showing a different website to users is something really nasty.
HN is a moderated discussion group that's intended to promote curious discourse. As such, community members may flag submissions and comments (if they have enough karma, and no, I don't remember how much karma you need for each). It's not perfect, but that's the intent. AFAIK, everybody has the ability to downvote. That's how moderation is done.
A link aggregator that can decide which links to show.
It wasn't anything controversial just a video showing unsolicited connections made by firefox, to support my theory that browsers developers contribute to mass surveillance.