Comment by lisper

> if the deduplication isn't atomic with the application's actions, incorrect behavior results

So? What do the application requirements have to do with the question of whether or not exactly-once delivery is possible? The application is a red herring. Why do you keep bringing it up?

If you want to argue that exactly-once delivery is generally undesirable, that is not in dispute. What is in dispute is whether or not it is possible, and the application requirements cannot possibly have any bearing on that.