Marlow is a character in many works, most famously Joseph Conrad's "Heart of Darkness." To help me understand your question, please provide the following information:
* Which work are you referring to? (e.g., "Heart of Darkness," "Lord Jim," etc.)
* What specifically troubles you about his diction? Is it the vocabulary he uses, the way he constructs sentences, the tone of his voice, or something else?
Once you provide more context, I can help you explore the troubling aspects of Marlow's diction and their significance within the work.