Is that possible? I remember that it was possible one day. As far as I remember, there was a "helpdesk" item under "Forums". Currently, there isn't one:
It is not possible to see the list of all HD requests in the public interface, because support agents should work from agent interface.
But, it is still possible if you have a direct link to the request (from email) or if user open list of his requests in the user's profile.
Support agents should work from agent interface, because it does have specific features for agents,