Hi @Jurgen0
Sorry you had this situation with your guest. Personally as a guest booking a whole listing and unless it was clearly stated that the host keeps some of their clothes at the apartment (which you don't), I would have been pretty surprised to see your clothes hanging in the wardrobe.
Having said that, it's not a reason for a refund and if this was his only complaint I would get on social media to Airbnb and publicly complain that a guest stayed for four nights and was refunded in full because you had a couple of jackets hanging up in the wardrobe. I would also call CS morning and night to ask why the guest was refunded.
Personally in your situation I would have been inclined to cancel this guest on arrival as it was clear your place wasn't a good fit.
I haven't had an issue with Airbnb CS in six year of hosting. I don't agree that Airbnb is US centric (look at the thousands of complaints from US hosts on here). Nor do I think it's appropriate to discriminate against any guests on the basis on which country they are from.
You mention you were awarded best apartment in your area - who gave you this award - I didn't know this was a 'thing' 🙂