Small caps

sc.js

(function () {
  var SKIP_TAGS = ['PRE', 'CODE', 'SCRIPT', 'STYLE', 'TEXTAREA', 'ABBR', 'KBD', 'SAMP'];

  function isInSkippedAncestor(node) {
    var el = node.parentElement;
    while (el) {
      if (SKIP_TAGS.indexOf(el.tagName) !== -1) return true;
      el = el.parentElement;
    }
    return false;
  }

  function scotf(root) {
    var walker = document.createTreeWalker(
      root || document.body,
      NodeFilter.SHOW_TEXT,
      {
        acceptNode: function (node) {
          if (isInSkippedAncestor(node)) return NodeFilter.FILTER_REJECT;
          return /[A-Z]{2,}/.test(node.nodeValue)
            ? NodeFilter.FILTER_ACCEPT
            : NodeFilter.FILTER_SKIP;
        }
      }
    );

    var nodes = [];
    var n;
    while ((n = walker.nextNode())) nodes.push(n);

    nodes.forEach(function (textNode) {
      var parts = textNode.nodeValue.split(/([A-Z]{2,})/g);
      if (parts.length === 1) return; // nothing matched

      var frag = document.createDocumentFragment();
      parts.forEach(function (part) {
        if (!part) return;
        if (/^[A-Z]{2,}$/.test(part)) {
          var abbr = document.createElement('abbr');
          abbr.textContent = part;
          frag.appendChild(abbr);
        } else {
          frag.appendChild(document.createTextNode(part));
        }
      });
      textNode.parentNode.replaceChild(frag, textNode);
    });
  }

  window.addEventListener('load', function () { scotf(); });

  // expose for manual re-runs on dynamically injected content
  window.scotf = scotf;
})();

Styling to use together with the script above.

abbr {
  font-variant: small-caps;
}