ok I'm gonna take a crack at this and you tell me if it's what you're talking about.
Sue Storms Invisibility, and Kitty Pryde's abillity to pass through walls would make this one person a ghost if they wanted to be.
Since B-list already refers to occasionally-obscure characters, I think anyone with their own monthly title(s) (i.e. Sue Storm) wouldn't be allowed at all. D-list, by any standardized definition, would have to be dudes that maybe Spider-Man has fought once or twice, or backup heroes on a villain team that inevitably get stabbed by Wolverine or something.
Still. Arbitrary distinction. I can't see a good definition emerging that will save this thread.
Demolitian man + paste pot pete + combo man + mole man
__________________ Quotes from Hia8:
"I claimed that the science is sometimes faulty."
"You don't understand. This is fiction. That means none of this stuff really happened."
"There is no writer to purposely ignore a character's natural ability just because it suits the story."
"in some cases because the writer knows that Character A will dominate Character B easily and refuses to allow this to happen for the sake of the story."
I'm closing this before it becomes a mess. Why not remake the thread with some more detail and maybe some characters as examples. Talk to Golem, he makes threads about the most obscure characters and gives us bios.