Problem styling author comments

I’ve been tweaking a theme and am almost done, but I cannot get the author comment styling to apply for some reason:

Comment code:

<div class="<?php if ($comment->user_id === $post->post_author) echo 'authorcomment'; else echo 'thecomment' ?>" id="comment-<?php comment_ID() ?>"></div>

<div class="comment-body"><?php comment_text() ?></div>

CSS:

.authorcomment {
	margin: 10px 10px 10px 10px;
	background: #dae7a2;
	border: 1px solid #336600;
	font-size:12px;
	overflow: hidden;
	height:100%;
}
.authorcomment .comment-body {
	border: none;
	margin: 10px 10px 10px 10px;
	background: #dae7a2;
	border: 1px solid #336600;
}
.authorcomment .comment-metadata {
	padding: 11px 10px;
	margin: 10px 10px 10px 10px;
	background: #dae7a2;
}

I’m no coding guru but I think it all looks okay, and yet the author comments aren’t showing their stylings in the actual blog – http://www.insanitytheory.net/kitchenwench

Can anyone tell me what I need to do to fix this up?