Final answer:
St John in 'Jane Eyre' is notable for his moral seriousness, missionary work, and his influence on Jane's understanding of her societal and religious duties.
Step-by-step explanation:
St John in Jane Eyre is a character distinguished by his moral rigor, missionary zeal, and somewhat cold demeanor, being more focused on duty than passion. He is an important figure in Jane's life, particularly towards the end of the book where he influences her perspective on religion and her role in society. The description of St John would include his role as a clergyman, his proposal to Jane, and his eventual departure to India as a missionary, showing his commitment to his work over personal desires.