It is not obvious to an author, if they can get committer +1 from a reviewer or not. This leads to reviewers being added, which in turn have no idea what button to press or how to respond.

It should be clear throughout the review process, who's able to do CR+1 and who not. E.g. the reviewers could get different colors in the UI, maybe already the moment they are added.

Optionally, if a non-committer reviewer is added on a CL, it would be nice if there was a formal response option for that person too.