I think below sentence is less encouraging and more direct. 
> Images should be built and managed by [maintable] Dockerfiles. If necessary however, changes in a container's file-system can be committed into a new image.

A recent discussion proved any action taken that forms a new layer can be and should be called a "commit", IIRC. 
This way, consistency between "commit" from a Dockerfile's command execution (which forms a new layer) and this can be sustained. 

But then I have a headache, so you should judge ;-)