Harry getting a howler in fanfiction often leads to intense drama. It could be a public humiliation, or it could trigger a series of events that change the course of the story. Maybe it makes him more determined to prove himself or it could cause rifts in his relationships with others.
Well, when Harry gets a howler in fanfiction, it might cause a big commotion. It could be from a family member scolding him for something he did or it could be a magical message with some urgent news that shocks him and those around him.