I have an SI2 diamond that from the pavillion side only has eye visible black spots that I was concerned about. Someone asked me if it was inclusions or debris. I do not know what debris is. Thus the above question... What is the difference?
I am just a consumer but I would say they are meaning debris as in dirt on the outside of the stone. There is no diamond grading term 'debris' as far as I know. If there is I am sure one of the experts will correct this. Inclusion as I am sure you know has many forms, feathers (cracks), crystals, pinpoints, black spots referred to as carbon spots (although I believe they are not carbon) etc.
I think the person saying debris means have you tried cleaning the stone, diamonds adhere to grease and lots of things stick to them like dust, grit etc. Often people mistake marks on the outside of the stone for inclusions.
Here's a PS thread you should check out. Diamond Bob from White Flash posts threads on various diamond topics. He titles his threads "Bob's Flashes". He recently did a post on "Dark Inclusions" that might address the "debris" question/issue for you.