Well I suppose they are called an Editor for a reason. They change the wording to reflect how they picture the character and might think that "What do you mean"

Well I suppose they are called an Editor for a reason. They change the wording to reflect how they picture the character and might think that "What do you mean" is too formal, even in England we are more likey to say "What d'ya mean". I guess the main thing was that Douglas Adams had the chance to review it and gave helpful feedback.