.echi is the CSS name for the comment count number tied to the comment hierarchy DW came up with for numbering comments, so that the first comment is 1, then 1a, then 1aa, and so on? You can explicitly turn it on here.

Code example from one of my comment pages:

<h4 class="comment-title"><span class="echi">1a.</span> 
<a title="Re: Agreed" href="http://marahmarie.dreamwidth.org/29154.html?thread=7650#cmt7650">
Re: Agreed</a></h4>

But I noticed looking at this again that each entry on a particular day is not in its own dd, which it should be.

Never realized that myself, will have to check it out. Thanks for the heads-up. :)