When you've completed the game, you can start a new playthrough with developer commentary enabled. If you haven't beaten the game, be warned that some commentary may spoil puzzle solutions.

In this chamber, you'll find a commentary node from:

Next to the piston with an orange portal above it.

[Nick Maggiore] Early versions of Portal featured more detailed, cluttered environments, much like Half Life 2. We quickly realized that unnecessary objects scattered all over the place distracted players to the point where it actually interfered with the portal training process. So we simplified the art style to favor clean, focused test chambers. The modular approach we settled on makes it look plausible that the chambers can reform dynamically on these pistons.