What would happen if I were to use a Hibernate class as a superclass without using any of the inheritance annotations built into Hibernate? Would the subclass be a regular old POJO?
The JPA specification more or less says that if an entity extends another entity is, it is connected through JPA inheritance. The default inheritance is always SINGLE_TABLE inheritance.
If the subclass is not annotated with @Entity, it’s not an entity in JPA terms, so this would be fine.