'opening poster' badges for MacRumors Forums with XenForo

// ==UserScript==
// @name        'opening poster' badges for MacRumors Forums with XenForo
// @namespace   http://forums.macrumors.com/*
// @version     1
// @grant       none

/* http://forums.macrumors.com/posts/21472342 */
/* http://forums.macrumors.com/posts/21481572 */
/* http://pastebin.com/5yKmk1WD for a companion style */

function displayThreadStarter() {
    var pageDescription = document.getElementById('pageDescription');
    if(pageDescription == null || pageDescription.getElementsByClassName('username')[0] == null){return;}
    var originalPoster = pageDescription.getElementsByClassName('username')[0].innerHTML;
    var posts = document.getElementsByClassName('message');
    for(var i=0; i<posts.length; i++) {
        var post = posts[i];
        var poster = post.getAttribute('data-author');
        if(poster == originalPoster){
            post.getElementsByClassName('userText')[1].innerHTML += '<em class="userBanner wrapped" itemprop="title" style="background: rgb(84, 191, 86);"><span class="before"></span><strong>opening poster</strong><span class="after"></span></em>';
        }
    }
}
displayThreadStarter();