Found a few problems with this section:
https://docs.docker.com/reference/builder/#environment-replacement

Note: prior to 1.3, Dockerfile environment variables were handled similarly, in that they would be replaced as described below. However, there was no formal definition on as to which instructions handled environment replacement at the time. After 1.3 this behavior will be preserved and canonical.

... there was no formal definition on as to which instructions handled environment replacement at the time

1. This sentence doesn't make sense.

Dockerfile environment variables were handled similarly
2. Similarly to what? Perhaps the note block should be moved after the explanation of Environment variable.

Perhaps someone could review the Environment variable section and reorganize the material presented.