I think some eBayers like to increase their feedback stats but simply can't be bothered returning the courtesy. Others withhold their feedback in case they need to retaliate for feedback they receive.
As a buyer, as long as you pay in a timely manner haven't you held up your end of the contract? The seller should then post feedback accordingly at that time.
As a seller, once your item has been received and the buyer is happy with it then the appropriate feedback and DSR's are posted. I don't think that anything that happens at that point changes the fact that the buyer has already fulfilled their part. There's no need to hold feedback hostage until the buyer posts it.
Just my 2 cents (Cdn).
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