Ah, bollocks - I just wrote a great long reply, and the interpipe ate it.
Ngah.
Potted version: The Black Dossier is set in 1950s Britain, but it gives centuries of backstory for the LoEG-verse. Nemo only crops up fleetingly in flashbacks - it's pretty much All About White People. Which is understandable, since most of the Western Canon is all about white people, and a fair bit is overtly racist too - which Moore shows, and fair play to him.
But the Gollywog? I can see why they've done it - he's a fitting inhabitant of The Blazing World, not least because most white Brits genuinely weren't consciously seeing gollywogs as representations of black people - that's how totally and utterly Other the blackface dolls are. It didn't occur to me that they were supposed to be human.
But I found this blogger's perspective quite compelling.
Notwithstanding that, though, my GOD, it's a fabulous creation. (I've found Jass Nevins' annotations invaluable.)
eta
I'm not sure that "rehabilitate" is the right word for what Moore's doing with any of the characters
My understanding is that he's explicitly stated that this is his intention wrt the gollywog, a figure which has fallen into considerable disrepute in my lifetime. When I was a child, it was generally perceived (by white people) as an innocuous toy, on a par with a teddy bear. It was an iconic figure associated with Robinson's Jam, and you could send off for shiny enamel gollywog badges. Now it's generally seen as an expressly racist figure, and the gollywogs have been removed from new editions of Enid Blyton's Noddy books, and Robinson's Jam have kicked Golly to the curb as a figurehead. He is persona non grata.
I really DO think that rehabilitate is the appropriate word for what Moore is attempting to do with this character. I wouldn't use that term to describe his depiction of anyone else - and indeed, I enjoy the fact that he ISN'T whitewashing James Bond, or Bulldog Drummond. But I think that the gollywog is a problematic figure.
As such, of course, it does fit in very well with the whole idea of censorship and becoming an unperson.
With "wog" still being bandied around as an insult on a par with "nigger", I'm actually good with today's children NOT growing up with golliwogs, or being read Little Black Sambo. So...yeah. Problematic, I think.