Originally Posted by DaleDe
It should be noticed that ePubcheck3 is not designed only for ePub 3. There is only one current ePubcheck and it happens to be version 3 which checks both ePub 3 and ePub 2. It knows the difference and checks specifications accordingly.
Thankyou Dale, that is what I've been trying to tell everyone here.
Passing epubcheck validation isn't optional, it is a requirement of the IDPF standard.