undelete.user.js

// ==UserScript==
// @name        Powder Toy Undelete Removed Comments
// @version     1.0.1
// @description Undeletes comments that have been removed, using a weird data leak.
// @author      boxmein
// @namespace   http://boxmein.net
// @run-at      document-end
// @match       http://powdertoy.co.uk/Discussions/Thread/*
// ==/UserScript==

var injected = function() {
  $('<div class="btn btn-undelete" style="float: right; margin-top: -5px; margin-right: -32px;">Show</div>').appendTo('.Message .alert.alert-danger');

  $('.btn-undelete').click(function() {
    var el = $(this).parent();
    var id = el.parent().attr('id').split('-')[1];

    try {
      id = parseInt(id, 10);
    } catch (err) {
      return false;
    }

    // console.log('undeleting', id);
    var req = location.pathname.replace('.html', '.json') + location.search;

    // console.log('http request to', req);
    
    $.getJSON(req).done(function(data) {
      // console.log('received', data);
  
      $.each(data.Posts, function(i, v) {
        if (v.ID == id) {
          console.log('found!', i, v, v.Post);
          el.parent().html(v.Post);
        }
      });
    });
  });
};

function inject(f) {
  var d = document.createElement('script');
  d.innerHTML = '('+f.toString()+')();';
  document.body.appendChild(d);
}

inject(injected);