> In my experience a lot of people actually do think that it's case sensitive.
I don't think they really do. They may think case matters somehow, and so may be careful to reproduce the exact case that they used before, but I don't think many people would expect JohnDoe@gmail.com and johnDoe@gmail.com to be too different email accounts.
In the general population, how many people do you think understand that username (including an email address) probably isn't case sensitive but that password almost certainly is?
I don't think they really do. They may think case matters somehow, and so may be careful to reproduce the exact case that they used before, but I don't think many people would expect JohnDoe@gmail.com and johnDoe@gmail.com to be too different email accounts.