This is a security hole in my opinion and should be plugged by editing the lock screen ui layout:
#find these objects and set the visible property to false
object class="GtkLabel" id="note-tab-label"
object class="GtkLabel" id="auth-username-label>
object class="GtkLabel" id="auth-realname-label"
Actually I had to remove the entire child statement:
Basically just search for "vbox3" and delete the entire child object shown in the graphic below (or in otherwords everything you see below should be erased and removed from the file. (recommend making a backup in case you mess it up!)
linux, mint, customize, username, namethis, plugged, editing, ui, layout, vi, usr, screensaver, dialog, default, disable, quot, gtklabel, label, visible, can_focus, tab, xalign, translatable, use_markup, auth, span, realname,