The titles of the chapters are in third person, while the text itself is in the first person voice of Huck Finn. What does this literary device suggest about the argument that Huck and Twain are one and the same?

This literary device separates Huck and Mark Twain.  By making the chapter titles in third person Twain is disassociating himself from the story.  Twain acknowledges that the story is a fictional work and not an autobiography.  The difference from chapter titles to text refute the argument that Huck and Twain are the same person.