I agree although I can see value in a pjax style approach to get faster page reloads. As long as you preserve normal behaviour and url structure, this is usually a win-win.

EDIT - just checked and it does a moderately good job without javascript: "Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode."

This is probably an acceptable compromise. Just to clarify - I'm not arguing that everything should work with js disabled - just that it's a good litmus test for whether a website is fairly robust with regard to normal HTTP behaviour.

Discourse in general loads a lot faster than traditional bbs when you click links or try to view a specific post. So what's being gained is better user experience. I'm not sure I see the relevance of the underlying data structure... isn't email just a collection of documents too? Why is gmail a SPA?