Did You Pass Math? is a blogware plug-in that “restricts comment spam by throwing the commenter a simple math question.” It works about 100% of the time against automated coments. Unfortunately, it also works about 50% of the time against real coments. When it fails, it eats your comment. I think it fails most often around suppertime.
Here’s the scoop. Either include a nice, Dunning-sized scoop of rum raisin ice cream with your comment or write your comment in a separate app like Notepad or your word processor of choice, then copy and paste it into the comment field.