when cooking a whole chicken to make bone marrow soup with, should I remove the skin before or after cooking?
Removing after will be much easier as everything will just fall apart when the collagen has been dissolved out.
The skin has a lot of fat that will have to be skimmed or separated if left on.
I would leave it on since you are trying to get the maximum flavor from the chicken. It will definitely be easier to remove after it's been cooked compared to before. Passing on an advise from my mother about cooking whole chicken is to boil it twice, first time in plain waster, discard waster and start over with clean water and all the flavoring vegetables.