Looks like it checks for the referrer in main.js and adds the uppercase text-transform if you come from HN:

  let host;
  if (document.referrer) { host = (new URL(document.referrer)).host; }
  if (host === "news.ycombinator.com" || host === "lobste.rs") {
    let style = document.createElement('style');
    // let transform = host === "lobste.rs" ? 
    style.textContent = `
      body { text-transform: uppercase; }
      pre, code { text-transform: none; }
    `;
    document.head.appendChild(style);
    console.log("HN readers clearly can't handle the typing habits of the average trans girl.");
    return;
  }