(1) It's not a big deal but an Email address is not the same as a URL. I came across this when I was harvesting and rejecting based on email address which I suspect is where a space got entered in the database since my blog doesn't require an email address to comment. If you checked email addresses differently from comment body content we could write regexp's that better fit email addresses
(2) I don't know enough WP/PHP to know whether this is possible or not, but if a comment fails the blacklist checks, could you return an 4XX error code (with an option to send a 301 redirect back to the posting IP). It probably won't stop the comment spam but dead links might eventually get purged out of their spam database.
Thanks for all your good work, Fahim.