I’ve renamed wp-comments-post.php to a random string of letters and numbers: something like qxx21227A.php. I’ve also used the Apache rewrite in an .htaccess file in my blog directories.
We’ll see if it works.
I’m having the same issue. Is it Partypokeronline? I’ve got my blogs set up so that all comments have to be approved by me before showing up, but I’m sick of playing Whack-A-Mole.