For the main post, there's another reason it's at such a high negative ranking: for the first day or two, the vote counter was not visible. That's when I added my downvote. It could have already been at -35 when I voted, but there's no way I could have known. I don't add a downvote to stuff that's less than -10 already.

It was at -20 when I first saw it, with its karma showing clearly, and is now at -39. So perhaps you do not vote things down that are already at -10, but at least 19 people do.