tampermonkey_script.js

// ==UserScript==
// @name         X mute the muted
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://twitter.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=x.com
// @grant        none
// @require      file:///Users/viktor/Developer/JavaScript/tampermonkey/xMuteTheMuted.js
// ==/UserScript==

xMuteTheMuted.js

// ==UserScript==
// @name         X mute the muted
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://twitter.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=x.com
// @grant        none
// @require      file:///Users/viktor/Developer/JavaScript/tampermonkey/xMuteTheMuted.js
// ==/UserScript==

;(function () {
  'use strict'

  const muteTheMuted = () => {
    const elements = document.evaluate(
      "//*[contains(text(), 'This Post is from an account you muted.')]",
      document,
      null,
      XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
      null,
    )
    for (var i = 0; i < elements.snapshotLength; i++) {
      elements.snapshotItem(i).parentElement.parentElement.parentElement.parentElement.parentElement.style.display = 'none'
    }
  }

  new MutationObserver(function (mutationsList, observer) {
    for (let mutation of mutationsList) {
      if (mutation.type === 'childList') {
        muteTheMuted()
        return
      }
    }
  }).observe(document, { childList: true, subtree: true })
})()