The reason why Xu Fengnian cut off his previous life was to get rid of fate, and to let the future and luck of Northern Liang get rid of the control of the Heavenly Dao. Cutting off his previous life meant that he had lost the ability to contact the Great Emperor Zhenwu, the Qin Emperor, and the Nameless Taoist. He could no longer ask their Dharmakayas to help him fight against powerful enemies. Although Xu Fengnian had increased his strength through hard work and gifts in the later stages, the decision to cut off his previous life had made his strength relatively weak. Cutting off his previous life's identity also allowed Xu Fengnian to get rid of the connection with his previous life in heaven, allowing him to face future challenges with his own strength.
The chapter where Xu Fengnian severed his previous life was not in the search results provided. It was impossible to determine the specific chapter where Xu Fengnian severed his previous life.
Goku might become more in touch with his Saiyan heritage. His tail was a part of what made him a Saiyan originally, so getting it back could make him more aware of his roots. He could become more aggressive in battle, like how Saiyans are known to be.
Well, in a lot of fanfictions, the story might rewrite the rules of the Dragon Ball universe. So Goku could keep his tail simply because the author wants to explore different storylines with a tailed Goku. Maybe the author thinks it adds more to his character's appearance and abilities, like being able to use it as an extra limb in combat or for balance during his super - fast flying.
Castiel's character development in these fanfictions can also be seen in how he views his loyalty. With his wings gone, his ties to heaven are severed in a more final way. This can lead to him re - evaluating his past actions and decisions. He may become more independent - minded, making choices based on his own moral compass rather than what heaven dictates. And as he struggles to come to terms with his new reality, he often emerges as a more complex and multi - faceted character.
The Joker cutting his face off is a symbolic act of completely letting go of any pretense of normalcy and embracing his insanity to the fullest. It's a shock tactic to terrorize and confuse his enemies.
Another possibility is that a new form of training or power - up in the fanfiction is related to the tail. So Goku is made to keep it for his growth and development as a fighter.
If Goku never lost his tail, his powers and abilities might have developed differently. Maybe he would have retained some primal monkey-like traits that could have given him unique advantages or disadvantages in battles.
He could be a martial arts instructor. Goku is a master in combat, and teaching others his skills would be a great job for him. He could train students in the ways of martial arts, sharing his knowledge and experience.