I tried to do a search for "Criticism of Alan Moore" and what I found was mostly that Alan Moore had been criticizing others, including Frank Miller, to who he owed much as Moore's WATCHMEN owed much to Miller's THE DARK KNIGHT RETURNS. But I did find a site with annotations for Moore's story in CINEMA PURGATORIO #9. This goes into some detail and describes a number of things in the story that I would otherwise not know of, which is not necessarily good.
It seems that some panels in this comic book story were redrawn from pictures in Donati's book with gruesome details added. One swimming pool photo shows corpses and sharks in a swimming pool ( evidently one that Thelma Todd is going to swim in, which was in Donati's book ). The commentary tells us that one body is Fatty Arbuckle, another seems to be Virginia Rappe*, and a third is Rudolph Valentino.
The commentary tells us that Arbuckle is dressed as a Keystone Kop and has an eye shot out. Having him floating in the pool brings to mind SUNSET BOULEVARD, but having an eye shot out is what happened to Bugsy Seigel. Whether Moore knows it or not, the interpretation that popular culture would put on that is that it indicates that this character was the victim of a mob hit. What Arbuckle actually died of was heart trouble. The entire business of having sharks and dead people in a pool that Thelma Todd is presumably going to swim in is strange and sounds like something a little kid would draw.
Later in the story it seems that there is a scene with an old man who appears to be dead, only nobody notices but a cat. What this has to do with anything, I don't know. Sydney Greenstreet is mentioned by the commentary. They could have put him in because he was in the 1941 version of THE MALTESE FALCON and Thelma Todd was in the original version, but that isn't stated.
Altogether a strange and unpleasant work by a strange and unpleasant author, and one that leaves matters no clearer than they were before it came along. It can't be said that it is really a serious attempt to do a comic book story based on Donati's book. I would call it a travesty.
*Moore claims in this story that Fatty Arbuckle was made the fall guy for Virginia Rappe's "lethally botched abortion"; I recall this story from one of the Fatty Arbuckle books, but that story has not actually been proven. This is the same sort of thing as telling everyone that Thelma Todd died accidentally when that hasn't actually been proven. Death is no joking matter. The death of Virginia Rappe was a tragedy the same as the death of Thelma Todd. And as Maltin said, the tragedy was not how it happened, but that it happened at all.
CINEMA PURGATORIO #9 notes: