I have successfully avoided having the entity manager persist entity changes when the user quits a conversation on purpose, by coding as follows:

@End
 @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
 public String quit()
 {
 logger.debug("Quitting without saving");
 entityManager.clear();
 return PAGE_MAIN;
 }

However, when the conversation times out, the entity manager is flushed anyway. So I added the following to the starting method:

@Begin(join=true, flushMode=FlushModeType.MANUAL)
 @TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
 public String startProcess()...

With flushMode set to true, in the method where I actually want persistence, I make sure to make a call to entityManager.flush();

Except any entity changes that are abandoned are still persisted after the conversation times out. What more must I do to keep the over zealous entity manager from persisting? And, larger question, why is this the default behavior?!