Around line 1459 you have get_post_author_title_link using the filter action of just "post_author_title_link" (without the get).
Since the display non-get function also fires the same filter, it performs the filter twice. Should instead be "get_post_author_title_link".
Oh and you broke a few of my plugins just by changing this function name used in the post.php template :-(
function post_author_title_link( $post_id = 0 ) {
echo apply_filters( 'post_author_title_link', get_post_author_title_link( $post_id ), get_post_id( $post_id ) );
}
function get_post_author_title_link( $post_id = 0 ) {
$title = get_post_author_title( $post_id );
if ( false === $title )
$r = __('Unregistered'); // This should never happen
else
$r = '<a href="' . attribute_escape( get_user_profile_link( get_post_author_id( $post_id ) ) ) . '">' . $title . '</a>';
echo apply_filters( 'post_author_title_link', $r, get_post_id( $post_id ) );
}
