The regular stock ComicPress does not include the Atom Feed in the so that browsers can recognize that there is an Atom Feed available (which is available on all wordpress installs)

In your header.php file find:

<link rel="alternate" type="application/rss+xml" title="<?php bloginfo('name'); ?> RSS Feed" href="<?php bloginfo('rss2_url'); ?>" />

And place this under it:

<link rel="alternate" type="application/atom+xml" title="<?php bloginfo('name'); ?> Atom Feed" href="<?php bloginfo('atom_url'); ?>" />