Same over-the-top patois. I've come to think that it's an indication that these characters are bound by vaudevillian stereotyped imagery of what is 'negro' (outdated word used intentionally). Jerome perhaps does it ironically, but Susannah as Odetta came from an upper income family, with no actual examples of blackness other than those of her class. When her personality split, she unconsciously relied on a stereotype to distinguish 'Detta' from 'Odetta'.