jQuery(document).ready(function() {

    var commentsLoaded = false;

    jQuery(window).scroll(function() {
        // Load comments when the Comments DIV is 600px below the bottom of the viewport
        var hT = jQuery('#comments').offset().top - 600,
            hH = jQuery('#comments').outerHeight(),
            wH = jQuery(window).height(),
            wS = jQuery(this).scrollTop();

        if (wS > (hT + hH - wH) && commentsLoaded == false){
            (function(d, s, id) {
                var js, fjs = d.getElementsByTagName(s)[0];
                if (d.getElementById(id)) return;
                js = d.createElement(s); js.id = id;
                js.src = "//connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.7&appId=475672159303398";
                fjs.parentNode.insertBefore(js, fjs);
            }(document, 'script', 'facebook-jssdk'));
            
            commentsLoaded = true;
        }
    }); 
});