Thanks for providing us with the additional information. It was really helpful in double-checking a few things. I'm posting out on the forum rather than directly replying just so both of us can help the general community in case anyone else bumps into this. Feeds are always tricky. When something is tagged with origin
ADWORDS rather than
USER, then it is as you noticed, a system feed. When that's the case, you usually can't make changes to it; there's a
bit more about that here. I appreciate that you're being a good citizen and attempting to move things over, but there are a few feeds that our system auto-generates, and the one you discovered happened to be one of them. You can just leave it alone; no migration is necessary. I would be surprised if it would even let you mutate it. If you find that it's causing you issues, then please get back to us, and we'll see what we can do to fix up that account for you.