I asked this question earlier today:
It was, in my opinion, well-posed but the answers made me realise that what I was asking was illogical. Of course, in the interests of the folk replying, it would not be good if I could delete the question as that would remove their gained reputation points. But I would like to signal to the community that the question is a poor fit to the knowledge base that SO is aiming to build: why should other folk be relied upon to do that? I would be willing to sacrifice a reputation point for the downvote for this sake.
Of course, upvoting your own question will lead to many problems, but I am not asking for that: just the ability to downvote.
I will, of course, be wanting to downvote this question too if it turns out that, on inspection of any replies, what I'm asking here is also illogical.