Thanks for the reply Achiel. Are there more of these hidden pages? And real funny, why does the unanswered page got page numbering? Why can't that piece not be incorporated in the main page? Would make the forum so much more usable.
We cleaned up the UI and removed a lot of those links: not many people were using them. However, the URLs still work. For instance: https://forum.mendix.com/questions/unanswered/ gets you all unanswered questions :)