Both websites could easily be done without JavaScript. I have built a blog and a site similar (without voting) to this using PHP/HTML/CSS when I was young.
HN works nicely without JS. With JS enabled it doesn't need to reload the page when you vote, so it's not necessary but still useful.
The problem are most other sites that often don't even load or show any content without JS support, or break in many creative ways. Although for weirdness you only need to disable custom fonts in the browser, and suddenly Reddit's notification button shows the Paypal logo and many websites have random chinese symbols scattered around the UI. And Google Translate looks like you need a translator to use it.
