I just got confirmation that Wattpad does have access to private messages and that they can also be used as a reason to ban an account! None of your "private" conversations are actually private!
Ignore User
Both you and this user will be prevented from:
Messaging each other
Commenting on each other's stories
Dedicating stories to each other
Following and tagging each other
Note: You will still be able to view each other's stories.