Answer:
The author is giving an direct characterization of the character speaking as an honest person.
Step-by-step explanation:
This is because "It must be understood that neither by word nor deed had I given Fortunato cause to doubt my good will." translates into modern english as such; You have to understand that I never gave any reason by speaking or actions for Fortunato to not trust me. This means that the character never gave any reason for Fortunato to not trust he/her. This means that this character is honest.