ALWAYS BACKUP YOUR FILES AND DATABASE BEFORE HACKING!!!
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Files to Edit:
inc/VIEW/users/_users_form.php
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OPEN inc/VIEW/users/_users_form.php:
FIND
$Form->text_input( 'edited_user_firstname', $edited_User->firstname, 20, T_('First name'), array( 'maxlength' => 50 ) );
$Form->text_input( 'edited_user_lastname', $edited_User->lastname, 20, T_('Last name'), array( 'maxlength' => 50, 'force_to' => 'UpperCase' ) );
$Form->text_input( 'edited_user_nickname', $edited_User->nickname, 20, T_('Nickname'), array( 'maxlength' => 50, 'required' => true ) );
REPLACE WITH
$Form->text_input( 'edited_user_firstname', $edited_User->firstname, 20, T_('First name'), array( 'maxlength' => 50 ) );
$Form->text_input( 'edited_user_lastname', $edited_User->lastname, 20, T_('Last name'), array( 'maxlength' => 50 ) );
$Form->text_input( 'edited_user_nickname', $edited_User->nickname, 20, T_('Nickname'), array( 'maxlength' => 50, 'required' => true ) );
EdB, go nag them to add this by default ;)