You've broken the site guidelines again with this. That's not cool. I'm not sure what to do besides repeat the explanation and links I just gave you.
> You can try to do the same with any other country, and you won't see this trend
Of course. That's the geopolitical battle of the moment. It was the same with Russia a year ago. All this shows is what controversy is hot right now.
> It's also very common for threads that are negative towards China to quickly disappear from the frontpage
Moderators routinely downweight hot controversies and political battles, as well as articles that repeat what has already been discussed recently. If we didn't, the front page would consist of nothing but that. Your mistake is in jumping to the conclusion that this has anything to do with our own political views or some secret bias about China. It does not. Our job is to protect HN from (a) mind-numbing repetition, and (b) earth-scorching flamewars. Why? Because those things kill intellectual curiosity, which is the point of this site. Everything we do as mods follows from that principle.
By the way, that last bit can be inverted to get a reliable test for moderator action on HN. If moderators do X, can you find a path from the principle of intellectual curiosity to X? If so, that's probably why we did it. If not, you can always ask us what the path is. We're happy to answer questions, but (again) as the guidelines say, it's better to send them to hn@ycombinator.com.