Hmmm — I wonder if that was a consequence of migrating from a site using Digress.it, rather than CommentPress. Unfortunately, though making the switch was easy, it doesn’t seem to have had any effect. Just for good measure, I updated the <i> and <b> to and as well, but no difference there, either. The comments are still invisible.
I wondered whether the <p class=”p1″> might be lurking in the comments as well, so I checked, but they all seem to be standard <p> tags.