code: function defaultFragmentHtml(fragmentName, faMarkdown, html, frame) {
  
      var f = generator.fragment$[fragmentName];
      if (f) return fragmentHtml(f);
  
      if (faMarkdown && u.find(opts.pkgs, function(pkg) {
        return ('pub-pkg-font-awesome' === pkg.pkgName);
      })) {
        return fragmentHtml( { _txt:faMarkdown, _href:'/#synthetic' }, {noWrap:1});
      }
      return /</.test(html) ? html :
        fragmentHtml( {_txt:html, _href:'/#synthetic' }, {noWrap:1});
    }
docs: try user-provided fragment, then faMarkdown with font-awesome, then html treat 3rd parameter as markdown if it doesn't contain <