Currently categories display its items as pagenames only. In some cases it might be better to show sortkeys instead of pagenames. For example its more understandable and easier to have
- Smith, Douglas
- Stevens, Arthur
- ...
than
- Douglas Smith
- Arthur Stevens
- ...
in category with persons only. And there are other cases across all Wikimedia projects where such behaviour would be better.
The best implementation would probably be by some magic word (like _DISPLAYSORTKEYS_ or other) or it could be switched dynamically.