To me, saying ‘please fill this out and mail it back to me’ is a command. Regardless of the ‘please’ infront, you are telling someone else what to do. Now it is a nice way of doing it, and may in all reality be totally appropriate for the situtation. But it is still a command. (And, as always, tone can make that polite ‘please’ into a sarcastic point and not nice at all, but it is still a command)
A non-commmand way of saying it would be something more like ‘Would you please fill out this form and mail it back to me’. Two more words, but now it is a question and the person being asked has a choice.
ie, “No, ill just drop it off tomorow.” This is an answer to the question, but not following the command.
