Captchas are the little letter codes that some sites require you to enter to prove you're a real human bean when trying to leave a comment.
And I hatesssss them. They are an abomination unto one's readers and I would never knowingly require one on any blog I set up. There are other ways of accomplishing the same thing (spam protection) that aren't so annoying to readers, and so totally destructive of accessibility. Hell, I've got reasonable vision and at least half the time I need a couple of tries at solving them.
Typepad added captcha tests a while ago as an option, but I've never turned it on here. To my horror, while testing comments to answer a question Riverdog had about Autocomplete, I found myself confronted with a captcha on my own site.
A help ticket has been dispatched poste-haste and the offender shall be banished. Sorry for the annoyance.
Here's an update explaining why Typepad won't let me get rid of the comment captchas altogether.