I just did it in 2 seconds on my other id-change from private to public-had to sign in again-it automatically defaulted to PUBLIC so no need to select option,clicked on save,showed a big green tick stating your feedback is now public & it is.

I did all that and also got big green tick, and signed out and in, and yelled at the computer, and it is still private.  It does not really matter, but as I bought the cooker accidentally on this ID, I thought I should show there is nothing to hide.  🙂