Try posting it again, or chalk it up to the winds of fate.
For the past week, I've noticed that the usually reliable comment spam filter we have in place here has been producing a much higher than usual number of false positives and negatives. Chinese splogs are showing up as potentially valid comments needing only approval, while comments from friends who've previously posted here are getting trapped with the metaphorical hair at the bottom of the sink. I even had to rescue a comment from one of my co-authors (evidently too obtuse to see for himself that his comment didn't appear immediately) from the filter.
Hopefully this will be fixed shortly, but if you've posted a legitimate comment or trackback here recently, and it didn't show up in due course, blame the gods, not us.