It's hard to say if it's common. There could be many people named 'bleach' out there, but we don't really know how many of them are fans of 'bleach' the series and also engage with fanfiction. It depends on how big the 'bleach' fan community is and how many people with that name happen to be part of it.
Mostly, it is legal to 'watch' (assuming it's in a form that can be watched like an audio - visual adaptation) Bleach fanfiction. Fanfiction exists in a legal gray area that is generally protected under the concept of fair use. This means that as long as the fan work is not competing with the official Bleach products in the market, and is more of a creative addition by fans for fans, it is legal. But of course, if the fanfiction starts to use copyrighted elements inappropriately or in a way that violates the original creator's rights, then it could cross into illegal territory.
I'd suggest looking on platforms like Comixology or Kindle. They often have a wide range of manga available for purchase and reading. Just make sure to check the availability of Bleach specifically. Also, some fan-run forums might have links, but be cautious as these could be against the law and of poor quality.
It's not that strange when you think about it. Naruto is a curious character. He might be interested in different stories and universes. Just like how we like to explore different fictional worlds, he could be intrigued by the Bleach fanfiction to see new ideas and concepts that he might not have in his own ninja world.
It can be normal. Many fans like to engage with multiple aspects of a fandom simultaneously. Watching 'Bleach' and reading its fanfiction can be a way to satisfy different cravings for the story. For example, the fanfiction might explore character relationships in more depth or present alternate plotlines that can be really interesting to compare with the original series.
It's not extremely common but it does happen. Some fans of anime in general are interested in exploring different fan - created stories across different popular series. Since both 'bleach' and 'naruto' are well - known shonen anime, there might be some overlap in the fanbases who like to check out what others have imagined in fanfiction.
One benefit is getting more content. The official 'bleach' might not cover all the possible storylines or character relationships that fans are interested in. Fanfiction fills that gap. Another is seeing different interpretations of characters. For example, a fan might have a different view on how a character should develop, and fanfiction can provide that.
One key feature is the unique perspective. Since it's about 'watching', it can offer a different view of the Bleach world compared to the original. Another feature is the potential for new storylines. Fanfic writers can create all kinds of new adventures for the characters.