Yes, in this fanfic Naruto has the extraordinary ability to heal anything. It's a cool concept that allows for all kinds of interesting plot developments. For example, he could heal the most severe of injuries that would otherwise be fatal, or even repair damaged landscapes. It gives the author a lot of room to explore different scenarios and challenges that Naruto can overcome with his healing power.
Well, it could be that in this fanfic, Naruto has developed a new jutsu that allows him to analyze and then replicate the DNA - like aspects of bloodlines. He might be using his vast chakra reserves to fuel this ability. For example, if he encounters a bloodline with a special element - like the Ice Release of the Yuki clan - he could break down the chakra signature and recreate it within himself.
Well, in fanfic, Naruto has the potential to create anything. The whole point of fanfiction is to explore different scenarios and expand on the existing universe. Since Naruto has strong chakra and is a very creative ninja, fanfic authors might let him create things like new villages or even new dimensions. It's all about taking the character to new and exciting places.
It implies that Naruto becomes a sort of deus ex machina in the fanfic. Since he can heal anything, he can solve many problems easily. This might make the story less tense in some ways, but it also opens up new opportunities. For instance, he could heal the wounds of a broken society or a damaged environment. His ability could also attract enemies who want to either use his power for their own gain or stop him from having such a powerful ability.
It could be Orochimaru. Since he's always interested in kekkei genkai and bloodlines, he might oppose Naruto when he discovers Naruto's new ability to copy bloodlines. Orochimaru would see Naruto as a threat to his own plans of collecting and using powerful bloodlines.
Well, one popular 'copy ninja Naruto fanfic' could be 'The Copy Ninja's New Adventure'. It often has Naruto using his copied jutsu in really creative ways in new and uncharted lands. Another might be 'Copy Ninja: Redefined' where he not only copies jutsu but also improves upon them in unexpected ways.
One possible reason could be a powerful jutsu gone wrong. Maybe he was hit by an enemy's attack that was specifically designed to numb his senses. Another reason might be some kind of psychological trauma. For example, if he witnessed something extremely horrible, his mind might have shut down his ability to feel as a form of self - protection.
In fanfiction, the world of Naruto is often expanded upon. Regarding Naruto's ability to copy jutsu, it can be a central plot point in some stories. For example, a fanfiction might have Naruto encounter a powerful enemy with a jutsu he's never seen before. His ability to copy it could be the key to his victory. Or perhaps the fanfiction explores the consequences of Naruto copying too many jutsu, such as losing control of his chakra or having his own identity as a ninja become muddled because he's using so many different copied techniques. There are countless possibilities when it comes to Naruto's jutsu - copying ability in fanfiction.
It could be Orochimaru. He's always been interested in experimenting on strong ninja. Naruto, being the main character, would be an interesting target for Orochimaru to mess with and cause this condition.
The 'copy ninja Naruto fanfic' is appealing because Naruto's ability to copy jutsu is so unique. It allows for all kinds of creative storylines. For example, he can combine copied jutsu in new ways.