Originally Posted by SpicyM

You don't need model release to claim autorship, nor you need model release to prove it.

You become author the moment you created something and should mark you work.

If he watermaked his video, the watermark is an identification of the author, so he is the author unless someone elses PROVES otherwise. So.. if someone published a video with watermarks cropped off, it is his DUTY to prove his authorship as he edited the originally marked work.