Karma rewards extrinsic behaviour, there's no reward for just logging in and reading stories on HN. I think that explains why some are members for 2 years, com

Karma rewards extrinsic behaviour, there's no reward for just logging in and reading stories on HN. I think that explains why some are members for 2 years, comfortable in reading the content on the site and contributing rather rarely when they have something insightful to say, while others are able to reach the threshold for down-voting in short periods of time without fully understanding the community or reading the guidelines.