On a video page, run this in the console, or click the bookmarklet, to have the comments sorted by their upvotes

sort-youtube-comments-bookmarklet.js

javascript: function findNodes(el) {
  return el.querySelectorAll('#vote-count-middle');
}

function isDigit(str) {
  return str.length === 1 && str.match(/[0-9]/i);
}

function metricVal(el) {
  let modifiers = {
    K: 1e3,
    M: 1e6,
    B: 1e9,
  };
  let text = el?.textContent?.trim();
  if (!text) {
    console.log('empty text', el);
    return NaN;
  } else {
    console.log('score found', text);
  }
  const match = text.match(/\d+(\.\d+)?[KMB]?/);
  if (!match) {
    console.log("bad parse " + text);
    return NaN;
  }
  const numText = match[0];
  let number;
  if (isDigit(numText[numText.length - 1])) {
    number = +numText;
  } else {
    number = +numText.slice(0, -1);
    const modChar = match[0].slice(-1);
    number = number * modifiers[modChar];
  }
  return number;
}

function compare(el1, el2) {
  let val1 = metricVal(findNodes(el1)[0]);
  let val2 = metricVal(findNodes(el2)[0]);
  if (val1 < val2) return 1;
  if (val1 > val2) return -1;
  return 0;
}

function nodeParent(node) {
  if (node instanceof DocumentFragment) {
    return node.host;
  } else {
    return node.parentNode;
  }
}

function findCommonParent(el1, el2) {
  const seen = new Set();
  let next = el1;
  while (next) {
    seen.add(next);
    next = nodeParent(next);
  }
  next = el2;
  while (next) {
    if (seen.has(next)) {
      return next;
    } else {
      next = nodeParent(next);
    }
  }
  return null;
}

function main() {
  let nodes = findNodes(document);
  let topNode = findCommonParent(nodes[0], nodes[1]);
  [...topNode.children].sort(compare).forEach(node => topNode.appendChild(node))
}
main();