The 200 Character Limit of the Offline Payment Instruction field is almost always too small, and should be dramatically increased.
One issue in Commerce that I've found to be frustrating that I imagine would be simple to address would be to increase the amount of space allowed for offline payment instructions in the final checkout screen.
Currently Commerce only allows 200 Characters, and this limitation has almost always been too little space to fit properly written instructions for nearly any payment method. I can only barely get the instructions for Check/Money order to fit, CashApp and Venmo can only be done with caveats. Proper instructions for International Bank Transfers or Wise foreign accounts wouldn't even be a practical consideration.
While this may see trivial, I would suggest that any information that needs to be conveyed to a customer in order for them to complete payment is not an area of an e-commerce site where one would look to save a few bytes of storage or transfer here and there if it compromises the optimal flow of the checkout process.
ideally every aspect of the checkout process should be clear, concise, and without ambiguity, and anything that isn't will likely only serve to reduce conversions.
I would personally like to see the payment instruction field be expanded to be able to allow a maximum of at least 600 characters, ideally 1000. This would allow for much more verbose instructions that would help to instill customer confidence in the checkout process.
I would suggest that the offline payment methods also either support HTML directly from within in the payment instruction area, or at the very least allow a QR code to be added that would also be printed on the customer's invoice. (Naturally the printed code would be variable in accordance to the payment type selected during checkout).
-Bryan