Given that enough people use this heuristic, there will be companies focusing on earning karma on HN, writing comments and voting for products they are getting paid for.
I bet the (niche) product as such wouldn't be as hard to build as it would be to scale. Imagine every user constantly tweaking (directly or indirectly) their search result settings, and having that impact millions (or more) indexed items, for every user.
You know how it works here. We would strip you of your internet points if you start being nonsensical.
The hn machine is not all that smart and can easily be gamed, and would, if the stakes were to become high enough. Farming hn karma by making pointed statements on crowd favorites (parent named two, oss licensing or privacy also spring to mind) gets you your 10k, no originality or honesty required, in no time.
What's protecting hn is a lot of moderation + relative irrelevance. If those 10k were to systematically bring you enough eyes (by driving search results), you are in effect printing money. There is no reason to assume the number of people doing it would not scale with the return attached to doing it.
Though I do not know how the initial allotment of karma/points could be distributed for the pioneers and for the new growing community, maybe allot 'n' points for new user after a year...
Playing defense is exhausting when playing offense is extremely cheap.
HN is quite a large crowd, but not extremely big. An attacker must penetrate a lot of small crowds to be successful.