Hi Leni
I'm not sure that selling for someone else exempts you from all (or any) responsibility - it does not work for auction houses, and it would not work for me if I advertise a cheap print in the newspaper as a Michelangelo original, and then claim " Sorry. Nothing to do with me Guv - I was selling it for a mate." You run the advert on eBay, you defend the statements in it. I don't see a court going any other way.
Placing 'spoiling' adverts might be helpful, but do the buyers of the dodgy items keep a keen look out for similar items? I suspect not. My elderly mother - Bless her little cotton socks - bought an 'original Lowry industrial landscape' off eBay. It may be a genuine Lowry - the jury is still out - but she did not go searching for others, to see if there was guidance about fakes. The idea it might be a fake had not crossed her mind. And that is a major point in trying to address the sale of fakes- the gullible punter.
I don't want to see people fall for scams. There is a German eBayer who regularly sells Baccarat millefiori 'design' paperweights, that are modern Chinese. He sometimes gets serious prices from them from unsuspecting, naive buyers. I have emailed him several times, but guess what, he is not interested in replying. I have reported him to eBay - deafening silence.
What else can you do?
Alan