The thing you have to know about Amazon is that they combine all the reviews for all sellers of the same product (to the extent that Amazon thinks it is the same product). As such, reviews aren't an appropriate place to leave feedback about a seller, and leaving your review up would have been misleading. The reviews are only supposed to be about the product.

You can leave feedback for sellers by clicking on their name in the listing.

This has pros and cons. It does allow you to see more reviews about the product you are purchasing, making it easier to find the gem reviews that are most helpful. On the other hand I think Amazon is too aggressive about combining reviews for similar but different products - different translations of the same book, different DVD sets of the same movie, etc. And seller ratings are deliberately not shown on the listing page, so few people click through to check the seller rating before buying on Amazon, let alone provide seller feedback.

I think the bigger problem is that the employees that rightfully deleted these reviews aren't required to instead migrate them to seller feedback, and forward them to folks that enforce seller policies.