Bloggers everywhere complain about spam comments that are not picked up by Akismet (or whatever anti-spam plugin they are using), but just as annoying for me are the comments that are not spam but include links to a dodgy web site.
They are annoying because they leave a decent comment but then insist on inserting a link to a questionable web site. I used to delete the link, and keep the comment, but they keep coming back and posting that damn dodgy link.
So I started deleting the comment but they still kept coming back and posting the same URL. Then I found a better solution, a solution that is actually very easy to implement because it is built into WordPress.
1. Go to Settings → Discussions
2. Scroll down to Comment Blacklist
3. Enter any URL, email address, IP address or words you wish to add to the blacklist.
And that is it.
Be very careful with which words you are going to block. Because it will not just block that word if it appears as an anchor text.