Annoying returners

RFW

Hoenir said:

I ended up marking my new items with an UV Pen.  As found that items were being purchased and returned as damaged upon opening. Given the fragile nature of the items. Very easy to damage when handling. The items I dispatched weren't the one's returned. 

How does marking them help? 
I'm not saying it's not a clever thing to do just wondering how that works in practice.

EffieTrinketsWig

I buy packs of uniquely numbered tamper proof labels from eBay and attach them to items that are at risk of being swapped and returned, I make sure that the labels are clearly pictured, there is no way to swap them or remove them without showing clear signs of tampering, especially useful for covering screw holes etc to prevent the internal parts of electronics being swapped.

savergrant

Hoenir said:

I ended up marking my new items with an UV Pen.  As found that items were being purchased and returned as damaged upon opening. Given the fragile nature of the items. Very easy to damage when handling. The items I dispatched weren't the one's returned. 

How did ebay respond when you reported that the wrong item had been returned?