First of all, great work on the plugin, I'm enjoying it.
I have the latest version of wordpress, and for the wordpress install I don't require the user to fill in a name or email (a checkbox on the discussion settings called: Comment author must fill out name and e-mail ).
This causes all of the comments to be labelled as spam under the 'empty' reason.
Looking into the code a little bit, it looks like you are checking if an email address exists for all submitted comments, which is obviously causing an issue since I don't require one.
Can you please look into fixing this bug for me.