But 99% of web applications are forms and displaying stuff. All JS accomplished is making it look prettier and enhanced tracking.
I mean, Facebook, my bank, Amazon… these can all be created with no client side code. It would be a lot of refreshes, but it can be done.
HN could too - perhaps the biggest use on HN is not refreshing when up (or down) voting something. YouTube could do something similar - refreshing when 'liking' a video or getting more comments. But would you really find those to be a better experience for you? Even on actions that HN does refresh on, such as 'Next page', or submitting a comment, HN doesn't freeze sorts, so posts and/or comments you didn't see will often invisibly end up before the new location HN sent you to (or posts/comments you already saw earlier in the list now showing up "again" later in the list).
Not saying that's exactly what should be done, but an example that there may be another way than full-on generic code execution wrapping XHR.
If you want a wildly interactive art experience, just load the appropriate browser for that.