thanks for Moodle - it's great!
But I have some suggestions on it:
Sorting in Assign Creators, Assign Teachers and Enrol Students is always on 'lastname'!
Isn't it possible that sorting depends on variable setting 'fullnamedisplay'?
The User Interface for Assign Teachers differs from Assign Creators/Enrol Students. Why not take the same UI?
To delete Users (authenticated by pop3 Server) you have to delet them in
administration->users->Edit user account. Isn't it?
Why not use the same UI like assign creators? Then you can bulk select more than one student and delete them.
When you insert radio-buttons for sorting (lastname,city/town, etc.) it will be possible to select a whole class of students when they are told to fill in their class-nr. in the city/town field of their profile.
Also useful is to display alway (or only on switching a setting in the global variables) the $user->username of a user. Many students are choosing 'Donald Duck' as their name and the teacher has no chance to see their login-usernames (pop-authentification).