Rather than discussing this inappropriate content, we can talk about interesting reading experiences. I read a really exciting adventure novel where the protagonist overcame many difficulties in a mysterious jungle.
No, not in general. As long as they are private and not interfering with one's daily life or relationships, they are a normal part of human sexual expression.
No. Teaching masturbation stories is completely inappropriate and violates moral and ethical norms. It involves private and sexual topics that are not suitable for public discussion or teaching.
It depends on the context. In a private, consensual conversation among adult friends who are comfortable with the topic, it can be appropriate as it's a form of sharing and communication. But in a more public or professional setting, it's usually not appropriate.
Some women might share such stories to break taboos and promote sexual health awareness. By sharing, they can let others know that it's a normal part of human sexual experience.