I agree with you. I buy lots on my other ID - so much that I probably make eBay more money from bidding up on items then I do from selling.
I hate it when I get a dozen similar items in the mail and many don't have any sort of invoice or indication regarding the sale. I try to give all feedback since that is my way of quickly checking through the list of purchases to see what has yet not arrived, but those that make my life difficult due to their laziness are judge accordingly in the communication component of the DSR. I firmly believe it is a lack of communication.
I communicate with all my sellers, to ensure that I can rate the communication component and that they send my purchase using stamps instead of metered mail - being that I'm a collector of postal history.