Hmm, you're experiencing some sort of javascript related problem. It's true that the "page 2" button on Qiaochu's user page (and similarly for any other user pages) does link directly to the URL you gave above. However, when everything is working correctly (e.g. as it does for me at the moment), a piece of javascript intercepts that click, and just reloads a small portion of the page (i.e. the list of questions) from the URL.
Perhaps you can try a different browser, clear your cache, etc., and see if you still have the same problem?
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