Comment by deanclatworthy

I'd suggest that your last point is providing a bad user experience in the interests of privacy. Many people (myself included) use these forms because we've forgotten our password or at worst forgotten the email we used to sign up. I have about 5 different email addresses I use for various things so I'd be quite disappointed to see a thank you message if it wasn't the email I had actually used to register. There's also the use-case where people mistype their email address.