arsewipe.js

const leftyTwats = ['theoldgreenfascist',
                    'DBC Reed',
                        'Liberal Yank',
                    'William Connolley',
                    'Don\'t Hug Me',
                    'Worstall\'s FAIL',
                    'Mister Bean',
                    'Heisenberg',
                    'mr ecks is a cock',
                    'Ecks is a fucking spastic',
                    'meiac',
                    'Jesus Christ',
                    'Newmania',
                    '3f1d756e98a2f6f2f036e7164635b5f8',
                    'Ice',
                    'Fatty',
                    'NiV',
                    't it',
                    'Steve.'];
const antiSemiticTwats = ['Dave',
                          'Davedave',
                          'Paul Rain'
                         ];
const justTwats = ['Rickie'
                  ];
const islamicTwats = ['Ahmed Fares'
                     ];

const themes = {
  'Worstall 2020': {
    comments: '//div[@id=\'comments\']/ol[@class=\'nv-comments-list\']/li',
    comment: 'article[@class=\'nv-comment-article\']/div[contains(@class, \'nv-comment-content\')]',
    author: 'article[@class=\'nv-comment-article\']/div[@class=\'nv-comment-header\']/div[contains(@class, \'comment-author\')]/span/descendant::text()',
    gravatar: 'article[@class=\'nv-comment-article\']/div[@class=\'nv-comment-header\']/div[contains(@class, \'nv-comment-avatar\')]/img/@src'
  },
  'Worstall 2007': {
    comments: '//div[@id=\'comments\']/ol[@class=\'commentlist\']/li',
    comment: 'article[@class=\'comment\']/div[@class=\'comment-content\']',
    author: 'article[@class=\'comment\']/footer/div[contains(@class, \'comment-author\')]/cite[@class=\'fn\']/descendant::text()',
    gravatar: 'article[@class=\'comment\']/footer/div[contains(@class, \'comment-author\')]/img/@src'
  }
};

const activeTheme = document.evaluate('//select[@id=\'theme-switcha\']/option[@selected]/descendant::text()', document, null, XPathResult.STRING_TYPE, null).stringValue;

function replaceDrivel (author, gravatarID, commentItem, twat, replace) {
  gravatarID = gravatarID.stringValue.replace(/.*\/secure.gravatar.com\/avatar\/([a-f0-9]+)\?.*/, '$1');

  if (author.stringValue === twat || gravatarID === twat) {
    const comment = document.evaluate (
      themes[activeTheme].comment,
      commentItem, null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null);

    /* Should just be the one, but replace all just in case */
    for (let i = 0; i < comment.snapshotLength; i++) {
      comment.snapshotItem (i).innerHTML = `<p>${replace}</p>`;
    }
  }
}

if(themes[activeTheme]) {
  const comments = document.evaluate(
    themes[activeTheme].comments, document,
    null, XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE, null);

  for (let i = 0; i < comments.snapshotLength; i++) {
    const commentItem = comments.snapshotItem (i);
    const author = document.evaluate(
      themes[activeTheme].author,
      commentItem, null, XPathResult.STRING_TYPE, null);
    const gravatarID = document.evaluate(
      themes[activeTheme].gravatar,
      commentItem, null, XPathResult.STRING_TYPE, null);

    [...leftyTwats, ...justTwats].forEach (twat => replaceDrivel (author, gravatarID, commentItem, twat, 'Usual twattish drivel'));
    antiSemiticTwats.forEach (twat => replaceDrivel (author, gravatarID, commentItem, twat, 'Usual anti-semitic drivel'));
    islamicTwats.forEach (twat => replaceDrivel (author, gravatarID, commentItem, twat, 'Usual terrorist supporting drivel'));
  }
}