Если запустить на странице с отзывами на товар на Яндекс.Маркете, соберёт остальные отзывы комментаторов и поищет интересные совпадения, когда разные люди оставляют одинаковые оценки на одинаковые товары или магазины.

yandex-market-check.js

javascript:(function () {
  function wait(ms = null) {
    return new Promise(r => setTimeout(r, ms == null ? (500 + Math.random() * 1e3) : ms));
  }

  async function clickWait(parent, query) {
    const e = parent.querySelector(query);
    if (!e) return false;
    e.click();
    await wait();
    return true;
  }

  function collectPageReviewersFromElement(element) {
    return [].map.call(element.querySelectorAll('[data-zone-name="product-review"]'), x => ({
      name: (x.querySelector('a[href^="/user/"][href$="/reviews"]') || {}).textContent,
      url: (x.querySelector('a[href^="/user/"][href$="/reviews"]') || {}).href,
      rating: +x.querySelector('[data-rate]').getAttribute('data-rate')
    })).filter(x => x.url).reduce((a, b) => ((a[b.url] = b), a), {});
  }

  function collectOtherReviewsFromElement(element) {
    return [].map.call(element.querySelectorAll('[href^="/shop--"], [href^="/product--"]'), x => ({
      name: x.textContent,
      url: x.href,
      rating: x.parentNode.parentNode.parentNode.querySelector('[data-rate]'),
      shop: /\/shop--/.test(x.href)
    })).filter(x => x.rating).map(x => ((x.rating = +x.rating.getAttribute('data-rate')), x));
  }

  const style = `#_scanPopup{ position:fixed;z-index:99999; top:0;left:0;bottom:0;right:0; background:rgba(0,0,0,0.5); }
#_scanPopup>div{ position:absolute; top:5vh;left:10vw;bottom:5vh;right:10vw; background:#fff; border-radius:4px;box-shadow:0 4px 10px rgba(0,0,0,0.5); padding:20px }
#_scanPopup>div>h1{margin-bottom:20px}
.loading:before{content:"";display:block;position:absolute;left:50%;top:50%;font-size:10px;text-indent:-9999em}.loader-animation-8 .loading:before,.loading:before{width:8em;height:8em;margin:-5em 0 0 -5em;border:1em solid rgba(0,0,0,.2);border-left:1em solid #000;-webkit-border-radius:50%;border-radius:50%;background:0 0;-webkit-animation:loader-animation-8 1.1s infinite linear;animation:loader-animation-8 1.1s infinite linear;-webkit-transform:translateZ(0);transform:translateZ(0)}@-webkit-keyframes loader-animation-8{0%{-webkit-transform:rotate(0);transform:rotate(0)}100%{-webkit-transform:rotate(360deg);transform:rotate(360deg)}}@keyframes loader-animation-8{0%{-webkit-transform:rotate(0);transform:rotate(0)}100%{-webkit-transform:rotate(360deg);transform:rotate(360deg)}}`;

  function setPopup(...content) {
    if (document.querySelector('#_scanStatus') == null) {
      const popup = document.querySelector('#_scanPopup') || document.body.appendChild(document.createElement('div'));
      popup.id = '_scanPopup';
      popup.innerHTML = `<style>${style}</style><div><h1>Hivemind Scan</h1><div id=_scanStatus></div></div>`;
    }

    const popupContent = document.querySelector('#_scanStatus');
    popupContent.innerHTML = content.join('');
  }

  function setLoadingPopup(...lines) {
    const html = lines.filter(x => x).join('<br>').replace(/\n\s*/g, '<br>');
    const existing = document.querySelector('#_scanLoading');
    if (existing != null) {
      existing.innerHTML = html;
    } else {
      setPopup(`<div style="position:relative;width:120px;height:120px;left:50%;margin-left:-60px"><div class="loading"></div></div><p id="_scanLoading" style="position:relative;width:400px;left:50%;margin-left:-200px">${html}</p><p id="_scanLoadingExtra"></p>`);
    }
  }

  function setLoadingExtra(...content) {
    const extra = document.querySelector('#_scanLoadingExtra');
    if (extra != null) {
      extra.innerHTML = content.join('');
    }
  }

  async function collectAllReviewers() {
    const reviews = {};
    updatePopup();
    await clickWait(document, `[data-apiary-widget-name="@MarketNode/ProductReviewsPaginator"] [aria-label="Страница 1"]`);
    do {
      Object.assign(reviews, collectPageReviewersFromElement(document));
      updatePopup();
    } while (await clickWait(document, `[data-apiary-widget-name="@MarketNode/ProductReviewsPaginator"] [aria-label="Следующая страница"]`));
    return reviews;

    function updatePopup() {
      setLoadingPopup(`Собираю список отзывов…`, `Собрано: ${Object.keys(reviews).length}`);
    }
  }

  async function collectAllOtherReviews(reviewerUrl, stepCallback) {
    var t = document.body.appendChild(document.createElement('iframe'));
    t.setAttribute('style', 'position:fixed;top:0px;left:0px');
    t.src = reviewerUrl;
    await wait();
    for (let i = 0; i < 5; ++i) {
      if (!await clickWait(t.contentDocument, '[data-apiary-widget-name="@MarketNode/UserReviews"] > div > button')) break;
      console.log('  Link to load more reviews is detected');
      stepCallback(collectOtherReviewsFromElement(t.contentDocument));
      await wait();
    }
    const ret = collectOtherReviewsFromElement(t.contentDocument);
    document.body.removeChild(t);
    return ret;
  }

  async function runProcessing() {
    const reviewers = await collectAllReviewers();
    console.log(`In total, ${Object.keys(reviewers).length} reviewers are found`);
    
    if (Object.keys(reviewers).length === 0){
      setPopup(`<p>Не нашлось ни одного отзыва. Это точно страница с отзывами?</p>`);
      return;
    }

    const summary = {};
    const currentProduct = location.pathname.split('/')[1];
    const productName = (document.querySelector('[href^="/product--"] h1') || {}).textContent;
    if (productName == null){
      setPopup(`<p>Не нашлось названия товара. Это точно страница с отзывами?</p>`);
      return;
    }

    let progress = 0;
    for (const [reviewerURL, reviewerData] of Object.entries(reviewers)) {
      updatePopup(reviewerData);
      console.log(`Processing ${reviewerData.name} (${reviewerURL}, review rating: ${reviewerData.rating})`);

      const otherReviews = await collectAllOtherReviews(reviewerURL, data => updatePopup(reviewerData, data));
      console.log(`  Loaded ${otherReviews.length} reviews left by ${reviewerData.name}, ${otherReviews.filter(x => x.shop).length} of which are for shops, average rating: ${otherReviews.reduce((a, b) => a += +b.rating, 0) / otherReviews.length}`);

      for (const otherReview of otherReviews) {
        if (otherReview.url.includes(currentProduct)) continue;
        otherReview.origin = reviewerData;
        if (summary[otherReview.url] == null) {
          summary[otherReview.url] = [otherReview];
        } else {
          summary[otherReview.url].push(otherReview);
          console.log(`  Intersection found: ${otherReview.shop ? 'shop' : 'product'} ${otherReview.name}, review rating: ${otherReview.rating}`);
        }
      }

      ++progress;
      updatePopup(reviewerData);
    }

    function updatePopup(currentReviewer, data = null) {
      setLoadingPopup(`Собираю другие отзывы авторов (${progress}/${Object.keys(reviewers).length})…`,
        data == null ? `Загружаю отзывы: ${currentReviewer.name}` : `Загружаю отзывы: ${currentReviewer.name} (уже загружено ${data.length})`);

      const ordered = Object.values(summary).filter(x => x.length > 1).sort((a, b) => b.length - a.length);
      setLoadingExtra(`<p style="white-space:nowrap;height:calc(45vh - 72px);overflow-y:auto;overflow-x:hidden;font-size:11px">${ordered.map(x => `<span style="display:inline-block;width:232px;margin-right:8px;overflow:hidden;vertical-align:bottom;"><a href="${x[0].url}" target="_blank">${x[0].name}</a></span><span style="display:inline-block;width:100px">${x.length} ${(x.length < 10 || x.length > 20) && x.length % 10 > 0 && x.length % 10 < 5 ? 'отзыва' : 'отзывов'}</span><span style="display:inline-block;width:100px">оценка: ${(x.reduce((a, b) => a += b.rating, 0) / x.length).toFixed(1)}/${x.sort((a, b) => a.rating - b.rating)[x.length / 2 | 0].rating.toFixed(1)}</span><span>${x.map(y => `<a href="${y.origin.url}" title="${productName}: ${y.origin.rating}\n${y.name}: ${y.rating}">${y.origin.name}</a>`).join(', ')}</span>`).join('<br>')}</p>`);
    }

    const ordered = Object.values(summary).filter(x => x.length > 1).sort((a, b) => b.length - a.length);
    if (ordered.length == 0) {
      setPopup(`<p>Не нашлось товаров и магазинов, отзывы от которых оставило сразу несколько людей 👌</p>`);
    } else {
      const amount = ordered.length;
      const isSingle = amount % 10 == 1 && amount != 11;
      const isMultiple = amount % 10 == 0 || amount % 10 > 4 || amount > 10 && amount < 20;
      const hasShops = ordered.some(x => x[0].shop);
      const hasProducts = ordered.some(x => !x[0].shop);
      const clean = Object.values(summary).flat().map(x => x.origin).reduce((a, b) => (a.includes(b) || a.push(b), a), [])
        .filter(x => !ordered.some(y => y.some(z => z.origin == x)));

      setPopup(`<p>${isSingle ? 'Нашёлся' : 'Нашлось'} ${amount} ${amount == 1 ? (hasShops ? 'магазин' : 'продукт') : [isMultiple ? 'продуктов' : 'продукта', isMultiple ? 'магазинов' : 'магазина'].slice(hasProducts ? 0 : 1, hasShops ? 2 : 1).join(' и ')}, отзывы ${isSingle ? 'которому' : 'которым'} оставило сразу несколько людей ${ordered.some(x => x.length > 3) ? '🤔' : ''}</p>`,
        `<p style="white-space:nowrap;height:calc(45vh - 72px);overflow-y:auto;overflow-x:hidden;font-size:11px">${ordered.map(x => `<span style="display:inline-block;width:232px;margin-right:8px;overflow:hidden;vertical-align:bottom;"><a href="${x[0].url}" target="_blank">${x[0].name}</a></span><span style="display:inline-block;width:100px">${x.length} ${(x.length < 10 || x.length > 20) && x.length % 10 > 0 && x.length % 10 < 5 ? 'отзыва' : 'отзывов'}</span><span style="display:inline-block;width:100px">оценка: ${(x.reduce((a, b) => a += b.rating, 0) / x.length).toFixed(1)}/${x.sort((a, b) => a.rating - b.rating)[x.length / 2 | 0].rating.toFixed(1)}</span><span>${x.map(y => `<a href="${y.origin.url}" title="${productName}: ${y.origin.rating}\n${y.name}: ${y.rating}">${y.origin.name}</a>`).join(', ')}</span>`).join('<br>')}</p>`,
        `<p>Остальные отзывы: ${clean.length}</p>`,
        `<p style="white-space:nowrap;height:calc(45vh - 72px);overflow-y:auto;overflow-x:hidden;font-size:11px">${clean.map(x => `<span style="display:inline-block;width:232px;margin-right:8px;overflow:hidden;vertical-align:bottom;"><a href="${x.url}" target="_blank">${x.name}</a></span><span style="display:inline-block;width:100px">оценка: ${x.rating.toFixed(1)}</span>`).join('<br>')}</p>`);
    }

    window['lastScanSummary'] = summary;
    return summary;
  }

  return runProcessing();
})();