I believe that the average is computed of all HN posts you have made. That means that it becomes harder and harder to change the average response, particularly

I believe that the average is computed of all HN posts you have made. That means that it becomes harder and harder to change the average response, particularly if you have posted a lot. Your performance is locked in by your history and the law of large numbers. It might make sense to have a time window on karma and have the average reflect the last 30 days or the last 100 posts or something of that ilk.