Are you referring to comments in blogs or to new blog setups? We scan the new blogs a couple of times a day to delete "splogs" which are created just for spamming. But unfortunately we have no way to scan existing blogs for comment spam. There are settings within each blog admin panel to help reduce comment spam, such as blocking comments that include even 1 link. Each blogger can set their comment rules in the blog admin panel.
Btw if anyone receives comment spam and you have your blog set to only allow comments from registered users, please send me the blogger username and I'll ban their account.
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