Create a document, write some text, then go to Edit->Changes->"record changes"
(in German: Bearbeiten->Änderungen->Aufzeichnen), then go to
Edit->Changes->"protect changes ..." (in German:
Bearbeiten->Änderungen->"Aufzeichnung schützen ...") and enter a password.
Then save the document, close it, reopen it, then enter some text, make changes
visible, then right-click on some newly entered text (which is highlighted as a
change) and you have the possibility to accept/reject the changes - without
entering the password! So after accepting, the information about who made the
change is lost 
=> protection of the changes does not work!