The key is to avoid long term pressure on the lid of the laptop.
In my student days, my laptop sleeve was always loaded into my bag closest to my body to reduce jostling it around. The pressure from the texts, notebooks, etc. pressing it to my body resulted in keyboard marks on the screen. At first they are minor, but eventually wear into the coating. It's just part of the deal.
Now that I no longer need to transport heavy texts, etc., I use a much smaller messenger bag. The laptop still goes in the corduroy-lined Timbuktu sleeve I've used since my 2008 white MacBook ($15 well spent). It then goes in the main compartment of my bag. If I decide I need to transport a large stack of papers or something, I'll use the padded laptop compartment in my bag for the laptop and place the documents in the main compartment. I've had my current M1 MBP since fall '21, and no permanent key marks yet.
If you choose to place something between the screen and keyboard, make sure it is thinner than the rubber gasket around the screen and you'll be fine.