In the very rare scenario that a package is damaged (beyond repair) in transit, then the buyer will be issued a full refund pending confirmation from the shipping service that the packaging was, in fact, compromised.
SidelineSwap puts the onus on the seller as far as packaging their items securely. Sellers should assume that their package will be thrown and shaken while in transit. It's on the seller to package their item accordingly.
It is SidelineSwap policy to defer to the designated shipping service for damaged package resolutions.