His creativity would likely expand. Since he's teaching himself fanfiction, he would start to view his own world from different perspectives. This could make him more empathetic towards others in the wizarding world as he tries to understand different characters' motives and feelings through writing.
One interesting aspect could be how Harry Potter might use his own unique experiences in the wizarding world to shape the fanfiction he writes. For example, he could write about his adventures with Hermione and Ron in a more creative and detailed way, adding elements that were left out in the original books.
One possible plotline could be Harry finding some ancient potions book in the library that has unique brewing methods. He then secretly practices them in an abandoned classroom.
Another challenge is that without a proper teacher, he may not fully understand the nuances of magic. Magic in the Harry Potter world has a lot of rules and ethics. Harry might accidentally break some of these rules while trying to teach himself. Also, he may not be aware of the proper pronunciation or wand movements for some spells, which could lead to ineffective casting.
In this kind of fanfiction, Harry could have an in - born talent that allows him to figure things out by himself. He might observe other wizards and witches casting spells and then try to mimic them in private. He could also have some sort of magical intuition that guides him in his self - teaching journey. For example, when he sees a spell being used for a particular purpose, he instinctively knows how to modify it for his own needs.
Snape could also be the one to teach Harry a lesson. Given their complex relationship in the original books, in fanfiction, Snape might see an opportunity to put Harry in his place. For instance, if Harry fails in a potions class because of his carelessness, Snape could use this as a chance to teach him about discipline and attention to detail.
Maybe Harry would teach Tom about the consequences of dark magic. Since Harry has faced Voldemort multiple times and seen the destruction caused by dark spells. He could use these real - life (well, in the wizarding world) examples to make Tom understand that there are other paths in magic that are more positive and life - affirming.
If he stabs himself in a non - vital area, he might survive but be severely weakened. This could lead to him having to rely on his friends more for protection and support, changing the dynamics of their relationships.
It could be due to the trauma he has experienced. Losing friends and facing Voldemort multiple times has surely left deep scars. Isolating himself might be his way of dealing with the post - trauma stress. He needs time alone to heal and come to terms with everything that has happened.