Right now, everything's in one column and that one column is clickable, which makes it difficult to quickly copy and paste details for multiple users.
Username and email address (clickable, can't highlight) | Permissions | Ban User
A sortable multicolumn approach seems more functional to me, something like this:
Username (not clickable) | Email Address | Join Date | Usergroup | Edit User | Permissions | Ban User
Sort by email address and search by email address seems to be lacking. There also needs to be a way to mass delete users, maybe a checkbox somewhere?
Added a mock up: