Docker was always intended to run in production. That was the goal from the beginning. The developers recommended against running it in production before the 1.0 release because it was in beta. Developers of many products that are intended to run in production do the same thing before the first stable version is released.

That is not the same thing as saying that Docker was never intended to be used in production, and was only ever intended to be a development tool. That's the view I'm arguing against, and it's not trivial -- it denies the fundamental purpose of Docker.