Sorry to interject. Good point about the internet. However, whilst a hoaxer might reasonably have assumed that the average Joe or Jane would be unlikely to subject the Diary to close analysis, surely they couldn't have expected the same response from respected JtR researchers, such as Paul Begg, Keith Skinner, and Stewart Evans.
There are murders that we are only even now discovering, John, with all the automation at our disposal. Besides, not every murder is recorded, some are not detected, there are anonymous victims of murder, and victims of murder who used pseudonyms or nicknames. Against that backdrop, even the stalwarts that you mention would struggle to prove conclusively that a made-up "JJ" and "MS" hadn't fallen victim to Maybrick-the-Ripper.