I'm a Chinese citizen, and ever since I started reading HN a few years ago, it feels like the media and comments in general are mostly negative towards China, or specifically to Chinese government. In rare occasions you have people trying to offer some different perspectives from someone who lived in China (like 1 out of 10 comments), but a large percentage of them get downvoted. This has not changed at all. So really, if there were a propaganda effort, it had failed miserably. The audience on HN just don't buy pro-China propaganda (for better or worse).

The ironic part about your argument is that whenever there is a positive news about China (like this one), it quickly derails into criticism of China.