On your private review page (what we call “offline reviews”) the reviewer can give any name he or she chooses and can even give a faulty or false email address – in which case you’d get a “bounce back” email when we thank them on your behalf, as this is from your email address as you know.
Once a reviewer goes through the next two steps (all of 10 seconds :)), every review site requires them to sign up with a name and their own email address or to log in with Facebook. So they can’t be “de-identified”. It’s to prevent fraudulent reviews.