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 platform that takes you to the elevator.

[Randy Lundeen] To make puzzles deeper than just teleporting to the exit, we had to include surfaces that won't hold a portal, which are formally introduced here. We experimented with several surface designs before we settled on this one, whose visual noise and reflectivity make it easy to identify at a distance.