Verifies show/hide HTML comments setting.
HTML comments shown:
<!-- comment 1 -->
- <html>
+ <head>…</head>
<!-- comment 2 -->
- <body>
- <p>
<span id="inspect"></span>
<!-- comment 3 -->
</p>
</body>
</html>
HTML comments hidden:
- <html>
+ <head>…</head>
- <body>
+ <p>…</p>
</body>
</html>