Just go to Blogger's feedback forum and post something like the following note as often as you can in as many related fields as you can and spread the word for others to do likewise (modify as needed):
The spam filter is a farce. It's an absolute joke.
Here's a link to what you claim isn't supposed to be happening:
Only Blogger can access this link because it's John Loftus's spam box. In in are 365 spam comments since August 26th from the same nutcase named DM. Almost all of them had to be manually marked as spam.
Some of them threaten his life.
It is NOT that much trouble to allow us to block IP addresses. We are adults. I demand the ability to block IP addresses with idiots like these just as newspaper editors have the legal right not to publish a letter to the editor.
John Loftus received over 50 of these spam comments today alone (September 24th)!
We will hound you about this. Individually we are nobody to you but together we will run a campaign about this if you do not do something about it immediately.
What would YOU do if this were you?
I am thoroughly frustrated about this.