I think it’s good that you don’t add sulfites, but I don’t think that’s why people feel bad. As you know American wine companies can and do put all kinds of things in wine (60+ different things) and not disclose. Whereas the EU has more restrictions on what can be added and what needs to be disclosed. Wine hangovers are often from additives, histamines, and sugar in sweeter wines. Sulfur sensitivity occurs in around 1% of the population