UPDATE: Artsy have not responded to the various points of malpractice set out below. I remain out of pocket. They seem mainly concerned with hiding the feedback behind a sudden flurry of 'invited' 5-star posts. Artsy have taken the trouble to block my account, with the result that I can no longer check details of my transaction history. Readers can draw their own conclusions.-----------------------------------------------------------Seemingly relaxed about corrupt trading on their platform, Artsy strikes me as the kind of player that gives art dealing a bad name. They turned what should have been a straightforward return of a mis-sold item into a months-long ordeal, and I have no reason to believe that the same would not happen again.I bought what was as advertised as an original, unique painting, by an artist whom I respected at the time. A week after delivery, I discovered by chance that it was neither original nor unique. It was actually a faithful reproduction, a plagiarized copy of another artist’s work, sold without attribution to the original artist. I made enquiries with the original artist; the copying came as a surprise to them, and they promptly referred the matter to lawyers.It turned out that selling gallery knew the painting was a copy; but, whether by negligence or fraud, they had not disclosed this in their advert on Artsy's site.Warning: Artsy allow sellers to doctor advertisements AFTER a sale has taken place. As soon as I raised a query, the gallery added a careful disclaimer to their advert’s fine print. They then refused further contact, and referred me to Artsy’s customer service team. They in turn rejected my complaint, claiming the doctored advert, with the added disclaimer, was the one that applied. Artsy put the onus on me to prove that their listing had been altered. I did indeed show them a print of the original version, but they dismissed this on the grounds that I could not prove to their satisfaction the date of the print.Persisting with the complaint, I met a wall of get-out clauses in Artsy’s policies. For example, they refused to investigate the mis-selling because I had reported it 8 days after delivery, not 7. They summarily closed the incident when I mentioned I had made a trivial adjustment to the back of the painting’s frame, because they do not accept returns of ‘altered merchandise’, whether legitimately sold or not.It was only when I put the suspected fraud to Artsy’s chief executive, by private email, that they bothered to investigate, and eventually accepted that the sale needed to be reversed. Even so, this took weeks to arrange.Multiple errors even in basic shipping documentation suggest to me that Artsy do not know what they are doing, or much care. For example, a missing Declaration of Authenticity resulted in me incurring EU import duty at 29% instead of 6%. I find I cannot reclaim this cost because, although the sale was annulled, and despite Artsy’s advertised returns policy, the shipping documentation had declared it non-returnable. Artsy blanked my requests for reimbursement, leaving me significantly out of pocket.I have no reason to think that the painting won’t be put back on sale on Artsy's site under the same misleading prospectus with which it was mis-sold to me. Artsy are either unable or unwilling to give me assurances on this, despite repeated requests.Thus, while I dislike giving negative reviews, I feel I should do this for the protection of other collectors. Unless/until there is a radical change in Artsy's systems and business model, avoid.