Yes you can also use this to block domain.com if you want. Because this is a full domain name, sites like otherdomain.com will be allowed to pass.
As for your suggestion, I wouldn't personally like this. I'd rather go with ESF, Blockcracking, spamassassin and RBL's to filter mail.
Because experience with hotmail has learned me that users are not always trustworthy to mark things as spam. I've had lots of users on for example hotmail, which declared "new post" notifications of forums or Wordpress sites and even birthday messages as spam, instead of just disabling their notification settings or ask the owner to remove their account.
So this could result in false positives of spam and maybe also hard to delist if it's indeed legitimate mail.