I know what you are talking about, Alan. I have seen that in other topics here. Basically the default is to omit the subject like in English. You can use the subject for clarity or emphasis if you wish. They both should be marked correct.
I have not yet been required to put in 'oe and have had all my commands accepted without it. Perhaps I have just been lucky. I don't know for certain that you can't use it, but the Tips & Notes and my experience in the course so far have certainly led me to believe that it is not required.