Although this isn't a perfect solution for us – given the constraints of the current DavServlet, the best I'm able to do in the way of a fix is to modify the code to display "display name (eid)" rather than just "eid". So just to be clear, if we're dealing with a student named John Doe with a display id of "jdoe" and an eid of "123", this will result in a drop box labeled:
John Doe (123)
The student will still be able to dav in using either
as per Nuno's original patch.
I'm attaching a patch to accomplish this versus the 2.5.x branch, which should be helpful for anyone who uses opaque eids and wants their maintain/instructor users to be able to recognize the member dropboxes.
One thing that QA will have to establish is that the spaces and parentheses aren't going to cause problems for certain dav clients.