There's no way to really tell if it's common specifically for someone named Jojo. However, in general, reading fanfiction is a popular activity among fans of many different franchises. The Jojo series has a large and dedicated fan base, so it's likely that there are fans named Jojo who partake in reading fanfiction, but we can't say for sure how common it is without more data.
Reacting to fanfiction can mean different things. It could be expressing your emotions like surprise, excitement, or disappointment while reading a fan - made story. For example, if a fanfiction takes a beloved character in a completely new and unexpected direction, you might react with shock or intense interest.
When we talk about'reacting to fanfic', it's a broad concept. It can be a very personal experience. Some people might react with enthusiasm, sharing the fanfic widely because they love how the author has reimagined the story. Others might react more critically, perhaps pointing out inaccuracies in the portrayal of the original elements. And then there are those who might have an emotional reaction, like getting really attached to a new character introduced in the fanfic or being moved by a particular scene in the story.
Perhaps this Jojo is interested in exploring different interpretations and stories within the Jojo universe that fans have come up with. Fanfiction often takes the existing characters, settings, etc. from the original Jojo series and creates new and unique storylines. So, this Jojo might be a big fan of the series and wants to see what other fans have imagined.
It depends. Maybe there are some telltale signs or elements that suggest it's a JoJo reference fanfic, but without specific context, it's hard to say for sure.