Now let's see if I've got this right.
A writer creates a character. Let's call him Joe Bloggs. If there is a real person by the name of Joe Bloggs out there, and he feels that the way character Joe Bloggs acts in the book tarnishes his name, he can sue the publisher of the book.
In theory then ... if a writer creates a character with his own name (as Paul Auster does The New York Trilogy for example) ... and that character acts in such a way that he injures the real life reputation of the author ... the author may then sue his own publisher for damages.
Worth trying if you're short of a few bob.