The translator will the default action for all incoming text, and display the translated text in the same format once it is received from the socket. Because of this, your highlight seems to be prevented from ever activating. However, if it didn't do this, you would be seeing 2 of every message. You'd probably have to add a highlight exception within the translation script itself, or change your highlight management to be in a script further up on the list than the translator rather than the built-in highlight in the address book.