Final answer:
The author described in the question is likely Ambrose Bierce, known for his unconventional writing and dark themes, and whose disappearance is considered an ironic twist of fate. Charles Waddell Chesnutt does not fit the description as his writing focused on realism and racial issues rather than dark poetry.
Step-by-step explanation:
The author who matches the description given in the question is most likely Ambrose Bierce. The description mentions a life ending in an ironic twist of fate and is associated with an unconventional writing style and dark themes—both characteristics that align with Bierce's life and work. Ambrose Bierce was known for his sardonic view of human nature and his works often contained dark and gothic elements. He disappeared mysteriously, which is often seen as an ironic twist of fate when considering the nature of his writing. Some of his famous works include 'An Occurrence at Owl Creek Bridge' and 'The Devil's Dictionary'.
On the other hand, Charles Waddell Chesnutt was a pioneering African American author who was associated with American Literary Realism. He did not end his life in an ironic twist nor is he primarily known for dark themed poems, which makes this description a mismatch for him. His works often dealt with issues of race in the American South and used dialect to give a voice to his characters. Therefore, the author in question is more accurately Bierce than Chesnutt.