It's easy to get comment karma, as well. You just have to be the first person to post the generally prevailing opinion on whatever the current topic is. Then everyone who was coming to post the same thing will just upvote you instead.
It's not that quantifying all of these things wouldn't be great, just that you very quickly will end up with a system way too complex to be reasonable.
At that point it becomes a video game, and loses any semblance of meaning anything whatsoever.