Scary stories might be seen as bad because they can overly stress or disturb some people's emotions. Also, for those who are very sensitive, it could have a lasting negative impact on their mental state.
It depends on what you mean by 'corpse reading'. If you just mean reading in a monotone or without much expression, it might not be the best for scary stories. Scary stories are all about creating an atmosphere, and the way you read can enhance or detract from that. If you read like a 'corpse', you won't be able to build up the tension and fear that makes these stories exciting. However, if you're just doing it for your own amusement in a private setting, it might not matter as much.
One common element is the unknown. For example, in many bad scary stories, there are things that lurk in the shadows or in places that are not fully understood, like a dark basement or an abandoned asylum. Another is the feeling of being trapped, like in a haunted house where the characters can't seem to escape the evil within.
There are many. For example, in one bad dream story, someone dreamed that they were on a small boat in the middle of a vast ocean. The sky turned dark and stormy all of a sudden, and huge waves started crashing over the boat. They were alone and helpless. Another involves being in a large, empty building with strange noises coming from every corner. As you explore, you find a room filled with dolls that seem to be alive and staring at you. A third one could be where you wake up in your own bed but everything in the room is distorted and there are strange creatures lurking in the shadows.
A man bought an old antique mirror. At first, he thought it was a great find. But soon, when he looked into it, he saw a face that wasn't his own. The face in the mirror started to change, becoming more and more distorted and menacing. Every time he passed by the mirror, the face seemed to be closer to getting out of the mirror world into his own.
The unexpectedness. We're used to proper grammar, so when we encounter bad grammar in a spooky context, it jars our senses. It's like something is off in the very fabric of the communication, which adds to the fear factor.
Once upon a time, there was a sign that said 'No enter'. A man ignored it and entered. Strange things started to happen. The room seemed to shift and voices whispered with wrong grammar like 'You no should be here'. He soon realized that the bad grammar was part of the curse in this place.
A popular story involves a young couple who used a Ouija board in their new apartment. They were just curious at first. But then the board started giving messages that seemed to predict bad things for them. They ignored it at first, but then strange things started happening around the apartment. Lights would flicker, and objects would move. They ended up moving out of the apartment because they were so scared. These stories might be exaggerated, but they sure are scary.
There was a story where a girl used a Ouija board alone at night. She asked if there was a spirit present, and the planchette moved to 'yes'. Then it started spelling out really creepy things like 'leave now'. She felt a cold breeze and got really scared. She threw the Ouija board away and never touched one again. It could be that the power of suggestion made her imagine things, but it was still a very scary experience for her.
The simplicity. 'Bad English' often uses basic words and simple structures. It makes the stories seem more primitive and closer to our basic fears. For example, 'There is a monster. It big and ugly. I scared.' It's direct and hits the fear center quickly.