Hi Brandon Haynes,
the Blog_Comments table already stores userID, only modifications to code would be required, take a look:

When a logged in user leaves a comment his DNN username is stored in the Author field, and userID in the userID field as well. When an anonymous user leaves a comment, the userID field is left NULL, and the name he provides is stored in the Author field.
Best regards,
Dario Rossa