"We all know that sensible posts get downvoted, just see this posting to confirm that."
If a sensible comment of yours has been downvoted, you might want to go to your comment history and check your other recent comments for downvotes. You might be the target of a Downvote Avenger!TM
With the rise of the Facebook Like generation I've noticed some people here engage in Downvote Revenge - I don't know what other term to use for it. Basically, something you post pisses someone off so much, they feel it necessary to assuage their anger by clicking to your post history and systematically downvoting all of your posts in sequence regardless of content, just to rack up your downvote count.
I've had it happen to me in the past; I noticed on one post a while back I got a downvote and a snarky response, and then a day later I suddenly had a single downvote on all several dozen or so posts previous to it. I can only surmise that one person had taken a dislike to me and wanted to show me what-for.
I consider that an achievement, akin to being able to punch someone in the face through the monitor. The more posts they take the trouble to go back and downvote, the more I know I've gotten under their skin and the more I enjoy the schadenfreude.
So go back and have a look at your post history. You never know; you might have scored!