In an attempt to block the flood of spammy comments, I've now enabled comment moderation (and, hooray, disabled the annoying comment captcha). This means I'll need to review your comments, though thanks to the way the system works, only your first comment will have to be manually approved (I hope).
You'll see a message to this effect when you submit a comment; I'll do my best to get to the queue multiple times per hour for today, just to see how it goes.
I know this isn't ideal, but it seems better than the broken captcha system that resets the captcha characters every time you preview.
Update: If you've published a comment in the last 18 months, you're now auto-approved, so you won't see a captcha, and your comment won't be moderated. This means it should be easier for you (instant comments!) and me (I'll only have to review new commenters' first submissions).
Mac OS X Hints