9gag_NSFW_loader.user.js

/* 9gag NSFW loader - Loads 9gag NSFW posts without login
 *
 * Copyright (c) 2015 Adrian Iain Lam <adrianiainlam@gmail.com>
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * A copy of the GNU General Public License can be viewed at
 * <https://www.gnu.org/licenses/gpl-3.0.txt>.
 */

// ==UserScript==
// @name        9gag NSFW loader
// @namespace   https://github.com/adrianiainlam
// @description Loads 9gag NSFW posts without login
// @include     http://9gag.com/*
// @version     1.0.1
// @downloadURL https://gist.githubusercontent.com/adrianiainlam/c382e9f971ed73262d6e/raw/9gag_NSFW_loader.user.js
// @updateURL   https://gist.githubusercontent.com/adrianiainlam/c382e9f971ed73262d6e/raw/9gag_NSFW_loader.user.js
// @grant       none
// ==/UserScript==

var baseurl = "http://img-9gag-ftw.9cache.com/photo/";
var jpgend = "_700b.jpg";
var gifend = "_460sa.gif";

function getImg(obj, postCode) {
  var img = document.createElement("img");
  img.onerror = function() {
    img.src = baseurl + postCode + jpgend;
  };
  img.src = baseurl + postCode + gifend;
  obj.innerHTML = "";
  obj.appendChild(img);
}

var scriptNode = document.createElement("script");
scriptNode.textContent = getImg.toString();
document.head.appendChild(scriptNode);

if(document.URL.indexOf("/gag/") >= 0) {
  var url = document.URL.split('/');
  var postCode = url[url.length - 1].split('?')[0];
  var obj = document.getElementsByClassName("badge-nsfw-entry-cover")[0];
  if(obj) {
    getImg(obj, postCode);
  }
} else {
  document.addEventListener("scroll", function() {
    var posts = document.getElementsByClassName("badge-evt badge-nsfw-entry-cover");
    for(var i=0; i<posts.length; i++) {
      var obj = posts[i];
      obj.className = "";
      var postCode = obj.parentNode.parentNode.getAttribute("data-entry-id");
      getImg(obj, postCode);
    }
  });
}

Don't know if you still maintain this, but the nsfw-class is now called "nsfw-post" and in your final 'if' a obj.className = "" would also be necessary because of the fixed CSS height attribute.

Cheers for the code!