Ask HN: After what karma can I downvote?
Are there any other features linked to the karma I have? Any page which lists them all?
The amount of gamification is minimal and has actually been reduced in the last couple of years when individual comment scores were hidden from public view. This is because, unlike Reddit, HN is not the end product. It is a marketing tool for Y-Combinator [the program], and to some degree a data stream useful for evaluating and filtering some of the applications into it.
To put it into perspective, historically, PG has been very much hands on to the point of rebooting the server, troubleshooting errors, and, of course, writing the code.
Let karma be its own reward, and to the degree you choose to pursue it let it drive you toward better writing things of interest to hackers.
One of the great opportunities HN provides is to write something and use the feedback [which may be no upvotes or downvotes] to improve your writing. HN is a great place to learn timing, tone, and how to tailor your message to an audience of readers. The path to higher karma which depends least on luck is posting thoughtful comments.
It's not 300, as said in another comment, because I'm over 400 and cannot downvote.