Positive features are worse than negative features. If there is a deep scratch there is going to be a positive feature typically around the edge of the scratch. I use a flat razor blade to cut these burrs from my platform once in a while and it cuts right through since the aluminum is soft and the burrs are thin. Some people use sand paper, plenty of methods available.
I think it has to be a pretty deep gash to make prints not adhere. A little bit of negative features would probably improve adherence to the platform since it gives shear geometry to grip onto.
Here is a previous Formlabs response: Sanding Build Platform Surface?