Restore the 'U' command back to "User Edit" and commented-out the
experimental 'U' (View Unread-Only toggle) command. The 'U' command from the e-mail menu (e.g. email_sec.js) works better than the toggle approach and is probably all that is needed. Also, the user number lookup in the User Edit bit is better at finding the proper user account (e.g. for received netmail).