I think it was pretty apparent that Mr. Norton had incestuous relations with his daughter which somehow led to her death. The thing that makes me curious is why Ellison included this in his book. But the fact that Mr. Norton was so fascinated by the story of the black sharecropper's incest with his daughter plus the fact that he later went into a sort of semi-coma seems to me that Ellison wanted us to think that Mr. Norton had incest with his daughter although this wasn't explicitly pointed out.
Another interesting part of the book was when the narrator worked at Liberty Paints and his first job there was to mix the "optic white" paint (Slogan was "If it's Optic White, it's the Right White"). In order to make the paint as white as possible, it has to be doped with a "jet black" liquid, which ends up disappearing into the paint, somehow making it even whiter then it was before. I think this was somehow symbolic of the black man becoming invisible to whites. I wonder if this is something that the author made up or if it really is true that white paint becomes even whiter if it is doped with a jet black liquid.
Anyway, things really got bizarre for a while when the narrator went downstairs with Lucius Brockway.