I think what I'd do is to make complete anonymity impossible. Access to the internet would always have to be traceable and evasion of this subject to a hefty fine for both the individual and the internet service provider. Then I'd establish a network of laws by international treaty to create a small claims court version of libel. In the UK anyone can make a claim in a small claims court for damages up to (I think) £30K for faulty product or services, or for failure to pay for them, without a lot of fuss, expense and lawyer, and without a significant financial loss if you lose. It ought to be fairly easy to extend this to a libel equivalent. That would ensure that what anyone says that's defamatory against another has to be defendable by evidence that would stand up in court or there would be a significant financial penalty.