This can be used to show the "latest updater" instead of the original Post Author. Adjust additional text to taste. I added spaces to separate the name from other info.

Show latest Post update person in Post Info

add_filter( 'genesis_post_info', 'dc_post_info_filter' );
function dc_post_info_filter($post_info) {
	$var = do_shortcode('[post_comments zero="No Comments" one="1 Comment" more="% Comments"]');
	$post_info = 'Updated by ' . get_the_modified_author() . '&nbsp &nbsp &nbsp' . $var;

	return $post_info;
}