Yes, but that's a problem with or without commingling. My point was that commingling doesn't contribute significantly to the counterfeit problem.

Regarding your points:

1. Amazon takes action when a brand complains, even with only a single complaint. Sellers have to prove the complaint is wrong to be allowed to continue to sell the product, or in some cases to be reinstated. Usually this is done by providing an invoice which Amazon verifies.

2. The enforcement is usually at the seller level, not the listing level.