I believe that your "Edit" hits the entire purpose of karma - encourage better writing. Karma for good posts. Karma for good submissions.
What is sometimes a struggle is that better writing is not always what we wish it would be. Sometimes is well reasoned explanations. Sometimes it is passionate argument. And often, highly rated comments and articles become highly rated because of timing. Sometimes it is just showing up (80% of the time, Woody Allen may have said).
It's satisfying to make a pitch perfect comment - even more so I find when it isn't snark or mean. I know what my best comments have been, and I know these are not the same as my highest rated. My best comments have been ones that I've cared about and some of those have even gone negative.
Do I really deserve that 69 points of karma? Is that 20 or 30 or 69 times more valuable than other posts where I've spent a lot more effort?
Perhaps this is where some of the 'snark' is coming from. In the race to get more karma, people are looking for the cheap throwaway one liner that everyone will snicker at and upvote.
Karma is probably more closely related to how popular your opinion is on a given subject in the hacker news community. As you said it does not really encourage better writing, while there is sometimes a correlation between a good post and many upvotes, especially on very technical subjects.
Also, Karma on news submissions has become a race to be the first to publish the latest techcrunch news or related sites, so it's not all about comments or contents.
What is sometimes a struggle is that better writing is not always what we wish it would be. Sometimes is well reasoned explanations. Sometimes it is passionate argument. And often, highly rated comments and articles become highly rated because of timing. Sometimes it is just showing up (80% of the time, Woody Allen may have said).
It's satisfying to make a pitch perfect comment - even more so I find when it isn't snark or mean. I know what my best comments have been, and I know these are not the same as my highest rated. My best comments have been ones that I've cared about and some of those have even gone negative.