Yes.
EBay does not use feedback to measure a seller's account.
Only Defects do that.
When you asked him to cancel the sale, he was allowed to do so without a Defect because Buyer Request is the only cancellation that does not get a Defect.
You are right.
Sellers are not allowed to raise the cost of shipping above the advertised rate*.
Feedback is an erratic method that allows buyers to tell other buyers how the transaction went.
There are limits on what Feedback can say. It may be that you overstepped the allowed limits.
The most effective FB is calm and factual. "Raised shipping after purchase Cancelled." for example, would be acceptable.
EBay does pay a lot of attention to Disputes and Claims. Those (along with seller-initiated cancelled transactions are what lead to Defects. And Defects mean higher fees, restrictions on the number and value of listings, and eventually even the closing of selling accounts.
a $2.50 flat rate shipping listed in his auctions meaning no matter how many you buy the shipping will be $2.50.
Go back and read the Shipping again.
Is there a price for additional purchases?
Does the $2.50 apply to Canadian buyers?
Does the seller say that he combines shipping charges?
And keep in mind that rates vary with dimensions, weight and distance, but not with value.
*It rarely happens, but a buyer could ask for a faster or better tracked service and be willing to pay the extra cost, in which case the seller could charge more. But that's one in a million.
