I think a major cause of the slowness is that all caching is explicitly disallowed by the forum - that’s why e.g. simply going back to the index from a post will cause a full reload of everything.

This is how much the forum is asking the browser not to cache each page:


Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Expires: Mon, 26 Jul 1997 05:00:00 GMT

In addition, the response time for loading each page is quite slow, particularly the HTML bits seem to simply take a lot of time to render on the server (while images, scripts, etc from the same server are not that slow).

In any case, if the caching headers were set somewhat sanely (like, at least allowing one minute of caching), I think it would make the forum feel a lot faster by letting the browser cache at least something. Less unnecessary reloading should also mean less load on the server and possibly faster responses overall (perhaps).