You can reverse the order of the comments beneath your Facebook posts by adding the following JavaScript to your site. This can be done manually using a custom JavaScript plugin. For further information see our documentation here.
$('.cff-item').each(function(){
var $list = $(this).find('.cff-comments-wrap');
var $listItems = $list.children('.cff-comment');
$list.append($listItems.get().reverse());
$(this).find('.cff-comment').hide().slice(0,4).show();
});