Content Approval Settings: Users aren't displayed with full name in the Group list

Description

Steps to reproduce:
1. Users (anng, hung, hana) with full name (An Nguyen, Hung Nguyen, Ha Luong) are available in the system. Anng and hana belong to WebAdmins
Admin user with administer rights on the page A.
2. Admin user selects pageA in page tree > Click Context menu.
3. Select 'Edit Approval Sequence' option.
4. Select 'Enabled' option in Approval Sequence screen.
5. Input 'we' into user textbox then select WebAdmins.
6. Move over WebAdmins.
Expected: A list of users belongs WebAdmins is displayed. Hana and anng users are displayed with full name in the list.
Actual: Hana and anng users aren't displayed with full name in the list.