Yes, Persona does reveal your email address to the website you log in to. This is considered a feature, because:
1. It prevents lock-in to Persona. (If you want to migrate away from Persona, you can just send the users an email and introduce the new authentication mechanism.)
2. Most websites will need some way to contact the user, and will ask for their email address any way.
3. Users understand the concept of email addresses as identifiers.
If you care about keeping your email address private, you can always use the features your email provider offers such as forwarding email addresses.
1. It prevents lock-in to Persona. (If you want to migrate away from Persona, you can just send the users an email and introduce the new authentication mechanism.)
2. Most websites will need some way to contact the user, and will ask for their email address any way.
3. Users understand the concept of email addresses as identifiers.
If you care about keeping your email address private, you can always use the features your email provider offers such as forwarding email addresses.