Sometimes it doesn’t matter how many safeguards you put in place to shield your online identity from defamation, negative copy can still get through. Once it does, you can go through all the legal channels there are and resolve the issue on that front, but you still have only won half the battle. As the old saying goes “What goes on the internet, stays on the internet”.
Someone not directly involved in the defamation can copy and paste all copy involved, all over the web. The person initially involved may not be able to post any more negative content of the nature that they did, and that original content may have been taken down, but there is the possibility that is is elsewhere on the net by the hands of someone entirely different.
What you can do now is check the internet yourself for copies of the content in question. First, get any applicable legal information you can and save it somewhere on your computer that you have quick access to. Then, take the content in question and run it through a plagiarism checking site. The good ones will show you where that content is on the web, or whether it is anywhere at all. They will go as low as 20% originality, which means that if the content was 1,000 words long and only 200 of them and have pasted somewhere else, the plagiarism checker will find it and tell you where it is with links you can follow.
From there, either leave a comment of your own that tells your side of the story, or get in touch with the owner of the site, with your legal information that you saved, and try to reverse what has been done to you on those sites. Nothing may get done on their end, but at least you know you have done all you could to perform damage control of your online reputation.