I'm the one that filed that report and just about fell out of my chair when I saw it marked "As designed" and "Resolved".
I would have to double check it, but the reason you can't delete the phrase is there isn't any id that links them to the navigation item. You need to know the full name of the phrase and delete it using that phrase.
The standard phrases for navigation items are...
Code:
FOR MENUS: vb_navigation_menu_' . $name . '_text'
FOR TABS: vb_navigation_tab_' . $name . '_text'
FOR LINKS: vb_navigation_link_' . $name . '_text'