Downvotes perhaps should have confirmations, because if you accidentally downvote, all you see is an "unvote" link. At times I'm unsure of which way I voted. I've taken to zooming the page large enough so that I'm confident that the right arrow has been pressed.

Doesn't it say "undown" instead of "unvote" when you downvote?

Oh, you're right!

Deletion already requires confirmation, and can't everything else be easily undone just as easily as it was done?

Can't you just "unflag"? Why would an undoable action require confirmation?