Despite dealing a lot on eBay, I didn't know exactly what you meant. I had only known about reporting non-paying bidders and had always wondered about reporting non-reliable sellers.
Anyway, I've finally sorted the thing out yesterday an got at least half of the shipping costs back, too. If you look at the time-frame, you see how long it took. On one hand, it makes me somewhat mad to have shipping costs declared as non returnable although the seller screwed up (see my post above), because the postal service won't return them to him. On the other hand, I have seen much, much worse and would even consider this a good outcome. Most people who do not know what a box is don't do too well in reasonable discussions about compensation, either. So I won't report anything. So, let me stop ranting (feels good to publically complain, though

@everybody:
I have ended up now with a battered up and incomplete SQ Trilogy. Anybody who is willing to pay for shipping can have it free! Take a look at it and see if it's worth it. Replacing the white box and adding some floppy disks might be easy.
http://www.vintagegames.net/public/sales/1050.html
I thought about posting this at the "For Sale" Forum, but I didn't want to double post. Also, it's a bit harder to find. Let's see who reads it first:)