after unchecked that "Keep Source format option" it should work. how u tired can u share your steps in screen shot?
correct me if i'm wrong, u don't want to keep comments filed at qliksense object and u simply want show in your nprint report only right? if so then u can remove that field from qliksense table object and go to your Nprint excel template & refresh your object and add dummy field in your excel template name called "Comments" then it should work. refer to the screen.