site registering vs WP autoresponder blog subscribers

I now have a registration on my page to be a user on the site and a seperate subscription link to subscribe to my blog. How can I make 1 do the work of both? I really dont like my users having to complete the registration because the 12 digit password they receive to confirm their registration is a pain. BUT, If someone subscribes to my blog without being a website register, they can’t post comments. AND if they register as a site user and not a WP autoresponder blog subscriber, i cant send an autoresonse to new users. Help?

Thanks,
Terri Lynn