jnrbsn on "RSS feed before the "more" tag"

I know this thread is a little old, but I think this is what you're looking for... Just add the code below to the functions.php file in your theme.

function mytheme_content_feed($feed_type = null) {
	if ( !$feed_type )
		$feed_type = get_default_feed();

	global $more;
	$more_restore = $more;
	$more = 0;
	$content = apply_filters('the_content', get_the_content());
	$more = $more_restore;
	$content = str_replace(']]>', ']]& gt;', $content);
	return $content;
}
add_filter('the_content_feed', 'mytheme_content_feed');

Remove the space between the '&' and the 'gt;' on line 10.