To get kicked off automatically, a seller would have to have a total feedback score of -3. Ebay does not know an item wasn't received unless the buyer files an item not received dispute. The feedback is only part of the transaction. If the buyer also gives the seller low DSR stars and the total stars fall below a certain point, the seller would be restricted but not kicked off. However too many item not received or not as described disputes could get the seller kicked off.
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Non payers should get unpaid item strikes and be added to block bidders lists. Period.