AFAIK the only functionality requiring JS on Hacker News is the up/downvote system. Comments open a new page anyway, so does editing. Wikipedia and issue trackers are the same, you only need to be able to GET and POST content basically. In terms of complexity it's very low.

You're right that they're not completely read-only documents but the interactive functionality is limited enough that it doesn't really qualify as an app. You don't need a client-side turing complete language to implement it, just forms. It's more akin to filling some paper form than interacting with Visual Studio if you see what I mean.

Very little on the web qualifies as a "web app" if the definition of that is, in essence, a simulation of a native application in the browser rather than merely an interactive document. But if that's the case, why are people upset about web apps "taking over" the document paradigm of the web?

Most of the web is still designed around displaying text. Even SPAs that require javascript to display text, for all the faults and valid criticisms that model entails, is still no less of a document in terms of its intended function than a bare HTML page.