twitter-l.js

// ==UserScript==
// @name         Twitter L's
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Replace Twitter Verified badge with a fat L
// @author       You
// @match        https://twitter.com/*
// @icon
// @grant        none
// ==/UserScript==

/**
 * @param {String} HTML representing a single element
 * @return {Element}
 */
function htmlToElement(html) {
  var template = document.createElement('template');
  html = html.trim(); // Never return a text node of whitespace as the result
  template.innerHTML = html;
  return template.content.firstChild;
}

function check(changes, observer) {
  var list = document.querySelectorAll('[aria-label="Verified account"]');
  for (var badge of list) {
    var altText = htmlToElement("<b style='background-color: #1DA1F2; color: white; padding-left: 4px; padding-right: 4px; margin-left: 5px;'>L</b>");
    badge.parentNode.replaceChild(altText, badge);
  }

  var xpath = "//span[contains(text(),'subscribed to Twitter Blue')]";
  var matchingElement = document.evaluate(xpath, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue;
  if (matchingElement) {
      matchingElement.innerText = 'This account takes a fat L because they paid for Twitter Blue.';

      xpath = "//span[contains(text(),'Verified account')]";
      matchingElement = document.evaluate(xpath, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue;
      if (matchingElement) {
        matchingElement.innerText = 'Verified L';
      }
  }
}

(function() {
  'use strict';
  (new MutationObserver(check)).observe(document, {childList: true, subtree: true});
})();