I like the offer feature.
It gives customers with a low budget the possibility to work with you files.
But offer spamming/trolling is bullshit!
https://3dartdh.files.wordpress.com/2016/08/a-troll-or-not-a-troll-that-is-the-question.jpg?w=1500
So this Brought me this two ideas, which could reduce this annoying problem.
1. Instant sale.
If the seller akzeptiere the offer, the sale is done.
2. Time limited sale.
After the seller accepted the offer the customer has one hour to cancel the sale.
And if the customer cancel the sale the seller will get a message.
And also the customer will be put on a list which counts how often he do cancel a offer just to analyse if it is a troll or a real customer.
Also the customer should know this by giving him a message/warning window which he must agree before he can do a offer.
Just some Ideas :)