kristopolous' console script is a godsend.  But, sometimes I like to just search for keywords without filtering others out.  Ctrl+f does the job but has issues such as losing my place after scrolling a bit, or not showing the searched terms anymore if I hit back after clicking a link, or not allowing for multiple keywords.
The following script simply highlights the word to make it a bit easier to find.  Also works well when combined with kristopolous'.  The output is the number of posts matching each input string.
  // usage:  highlight('react', 'node', 'graphql', '$')
  // output: [57, 29, 4, 19]
  function highlight(/* args */) {
    return Array.prototype.slice.call(arguments).map(function(keyword) {
      var matches = 0;
    
      Array.prototype.forEach.call(document.querySelectorAll('tr.athing.comtr div.comment'), function(e) {
        if (e.innerText.search(new RegExp(keyword === '$' ? '\\$' : keyword, 'i')) === -1) return;
        ++matches;
        e.innerHTML = e.innerHTML.replace(new RegExp(keyword === '$' ? '\\$' : keyword, 'ig'), '&lt;span style="background-color:#0095ff;color:#fff;"' + keyword.toUpperCase() + '&lt;/span')
      });
      return matches;
    })
  }
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