1. Do not display comment box if its not available
2. Instead, display text "To comment this page, you need set your email address on the options page. This is stored in the browser cookie, no password needed."
or even
2 b. Display email input field next to comment field if email is not filled in
1. Do not display comment box if its not available
2. Instead, display text "To comment this page, you need set your email address on the options page. This is stored in the browser cookie, no password needed."
or even
2 b. Display email input field next to comment field if email is not filled in