I can confirm that this bug has not been fixed while using doctrine 2.4
Exactly as Oleg Namaka has described, my organization is trying to use @PrePersist callbacks to enforce validation on new entities.
However, we use an extensive client side framework that sends json back to our server. Our workflow is then:
deserializeJson into detached entity
merge detached entity to get it managed (this will apply our edits to an existing entity, or create a new one if this one is new)
However, some entities run into the above problem while using this workflow, so our validation is not run. I can provide more code samples if required.