Since Karma Changes was posted, there have been 20 top level posts. With one exception, all of those posts are presently at positive karma. EDIT: I was using the list on the wiki, which is not up to date. Incorporating the posts between the last one on that list and now, there is a total of 76 posts between Karma Changes and today. This one is the only new data point on negatively rated posts, so it's 2 of 76.

I looked at the 40 posts just prior to Karma Changes, and of the forty, six of them are still negative. It looks like before the change, many times more posts were voted into the red. I have observed that a number of recent posts were in fact downvoted, sometimes a fair amount, but crept back up over time.

Hypothesis: the changes included removing the display minimum of 0 for top-level posts. Now that people can see that something has been voted negative, instead of just being at 0 (which could be the result of indifference), sympathy kicks in and people provide upvotes.

Is this a behavior we want? If not, what can we do about it?