I found a very simple plugin that says it will do this for posts, so I was wondering if a slight change to this plugin will do this for comments (show only the comments related to posts of that particular author).
By the way, I'm not sure if this plugin actually works for posts or not, but maybe someone with PHP knowledge can look at it, and it will spark an answer.
Found the plugin here: http://code.mincus.com/41/manage-your-posts-only-in-wordpress/
This is the code:
<?php
function mypo_parse_query_useronly( $wp_query ) {
if ( strpos( $_SERVER[ 'REQUEST_URI' ], '/wp-admin/edit.php' ) !== false ) {
if ( !current_user_can( 'level_10' ) ) {
global $current_user;
$wp_query->set( 'author', $current_user->id );
}
}
}
add_filter('parse_query', 'mypo_parse_query_useronly' );
?>