I don't recall this being discussed by the community at all. It seems like a bad idea. Valuable conversations can extend from comments that are already negative. -3 is also not that negative. This also discourages people from actually explaining why someone is wrong if there are a lot of people who downvote the comment. This will both make it harder for that person to become less wrong and make it more likely that bystanders who are reading the conversation will not see any explanation for why the comment is downvoted. Overall this is at best a mixed idea that should have been discussed with the community before implementing.
I don't recall this being discussed by the community at all.
This isn't terribly relevant. Moderators that discuss every decision with the community and only act when they've built consensus fail prey to vocal minorities, e.g., Wikipedia. Then they tend to stagnate.
Has anyone yet mentioned or reported that for the last couple days, the "karma for last 30 days" is showing zero for everyone? And that we no longer can see the top contributors for the last 30 days either?
Do we have an explanation or estimation for a bugfix on this?