Is the CF formatting after the firmware update really necessary, or removing the firmware file is enough?
Wondering about the same thing.
It isn't strictly necessary to format the CF (or SD) card after updating the firmware; you could just as easily remove the card from the camera, insert it into your PC's card reader, and there delete the firmware update file from the card.
I think Canon stipulates this instruction, as it's the simplest, safest and most straightforward method for ensuring that the firmware update file is removed from the card, and that the card is made ready for capturing more images / video, all without needing to remove the card from the camera.
When I put one of my cards into a card reader after capturing images to it, it has two folders, one containing images and a second named CANON_MISC (or something similar). I don't know if these folders are created during the format process, or when the first image is captured; I've never taken the time to check. But if they are created during the format process, it would be another reason for following Canon's recommended procedure, rather than, say, putting the card into your PC's card reader and formatting it there.