I've turned the CAPTCHA feature back on. (This is the twisty "word" you have to type in to post a comment.)
It appears that some spam bot found me -- fourteen "comments" were posted between yesterday and today. Deleting these is a laborious one-at-a-time process, and it's just too much of a pain to keep doing it.
I'll turn the CAPTCHA feature back off in a few days. Meantime, sorry for the inconvenience.