So let's say you sell a bag of a large amount of a certain type of circulated coin on ebay. You happen to then look at the buyers items to maybe reciprocate a sale and see they seem to be selling rolls of said coin with nice shiny unc examples poking out the end of the rolls. Then you look at feedback of buyer and see neutrals and negs claiming only end coins are nice and rest are worn circulated examples. Would you be suspicious that said buyer is seeding rolls and plans to use the coins for filler?
I wouldn't be suspicious. I'd be convinced. But, if you sold your coins fairly at a price reasonable to both you and the seller, you can't really dictate what he does with them. His dishonesty or deceitfulness is his problem.
"A funny thing happened on the way to the forum". I also play around on Listia, a trading site, your stuff for their stuff. I do a lot there in volume but nothing rare. I know my handwriting on my 2X2's very well and often see people relisting the stuff I traded out. I've always been very reasonable but then notice my stuff going for outrageous amounts. Each to their own as to how much they ask but I get laugh out of how these coins are relisted, their descriptions and the amount they ask for them.