Leave message in Checkout Flow

Exploring possibilities for a cleaner progressive disclosing order message input entry.

The checkout flow is the (almost) final touchpoint of a successful conversion in ecommerce thus every effort leads to a clearer and low-distractive checkout page worth a try.

The current page contains everything in listed format; it was detailed and well-explained at the beginning but may not work the same after new features added in.
Leaving message to seller is an optional feature and it's adoption rate is relatively low. Thus I plan to pack the component into a progressive snackbar component.

This is a demo of how it works. It's an ongoing attempt, all comments are welcome!