Metapost: Making it harder to leave comments

Sorry, folks, but deleting spam comments all day long is not my idea of blogging. I'm sure it's not what visitors come here for, either. So I'm compelled to make it just a teensy bit more inconvenient for you to leave comments.

I turned the "word verification" setting on. This means that when you post a comment, you'll be shown a little picture of wavy nonsense text and asked to type what you see. This is supposed to thwart automated spam generators.