Funny, I just made something like this today (but more primitive), mostly so that I won't miss Walter Bright's comments.

    // ==UserScript==
    // @name     Hacker News VIP highlighter
    // @version  1
    // @grant    none
    // @match    https://news.ycombinator.com/*
    // ==/UserScript==

    function highlightVIPs() {
      'use strict';

      const VIPs = [
        "WalterBright"
      ];

      const userTags = Array.from(document.getElementsByClassName("hnuser"));

      userTags.forEach(tag => {
        const username = tag.href.split("=")[1];
        if (VIPs.includes(username)) {
          tag.style.fontWeight = 'bold';
        }
      });
    }

    highlightVIPs();

(I'm not much of a JavaScript programmer, but it seems to work.)