1. I don't get it.
2. I have to wonder if Chambers, supposedly writing in the late 20's or early 30's, would have used the term 'black' to designate African-descended people. I know Scott Fitzgerald and Richard Wright did, but they used it as an adjective. Blish was alive in the 30's and I wasn't, so presumably he'd know. But would someone born in 1865 have written 'it should be noted that all the characters are black'? especially when he uses 'Negro' in the work he really did write?
3. And finally: James. Did you not read the stories in The King in Yellow? Did Chambers' own highly coloured style escape your notice completely? I might just- *just*- agree that possibly tKiY was not supposed to be a Jacobean play and that it *might* not have used iambic pentameter- though it'd have been a damned odd play if it'd flouted English literary tradition like that. But I doubt very much that if Chambers had indeed written a version of tKiY, it would have read like a chunk of mid-20th century journalistic prose with line breaks.
That said, however, it's diverting to google R.W. Chambers and find yourself reading that he was a friend of Tolkien's. Raymond Wilson, not Robert William.