One of my code reviewers had a watchlist where they CC their @chromium.org email, without +watch.

I couldn't add them as a reviewer until I deleted them from the CC list. There were about 10 CC entries from various watch lists making it not obvious.

Autocomplete didn't suggest their name until I deleted them from CC.
When I manually typed in the email address and pressed "Send" (with them in the CC list), the button clicked, the popup went away, and then they were not added as a reviewer.

It would be useful to see some sort of error indication that no email was sent, or allow the same entry to be in CC and review.

Here is the review:
https://chromium-review.googlesource.com/c/521753/