I don't think it's reasonable to quit a site because a post you feel is important suddenly drops in ranking. There are all sorts of reasons this could happen, with user flagging by a tiny number of individuals probably being the most likely. It's currently sitting at the top of Page 3: https://hnrankings.info/36187203/.
If you genuinely think rage quitting is the best response, probably this place isn't a good fit for you and you should just go. But if your goal though is to improve the site (and possibly the world) for the better, you could send email to Dan (hn@ycombinator.com) and ask what happened here.