The journal certainly hasn't been proved to be faked. Yes there are lots of sceptics, many of who have vested interests in maintaining the claim of their own preferred culprit. I've read two or three books about the diary and while it can't be said to be definitely the work of the ripper lots of...
Is the correct answer.
I havent read this latest theory but for me the most likely suspect was James Maybrick.
And I seem to remember reading that kosminsky was in jail somewhere at the time of at least one of the murders - or was that Tumblety?