Is hook_translated_menu_link_alter() thought to be used only on translated menu links? Could hook_translated_menu_link_alter() be implemented to simply alter a menu link before it is rendered?

Clearly, hook_translated_menu_link() is only invoked for menu items that have been flagged from hook_menu_link_alter() as altered; if a module uses hook_translated_menu_link() to alter a menu item before it is rendered, it needs to implement hook_menu_link_alter() too.
Take a look at Devel, it uses hook_translated_menu_link() along with hook_menu_link_alter() to add a destination query to the end of a few of the links.

http://drupalcode.org/project/devel.git/blob/0ca6cc9bd5e2cf650717b73e8938b88726d0ebbd:/devel.module


Line #331 - devel_menu_link_alter()
Line #342 - devel_translated_menu_link_alter()