Yes, exactly, which was very much the original point of the post! It's not about judgements of what large or medium or whatever should feel like, or how they relate to the average person, or whether people are in denial about their size, or how sizes have changed over the years. It's the annoying aspect of Vinted of equating two things that most people don't find go together - size 12 and size L - and the subsequent pairings of the other number/letter combinations. I don't care what the moral/statistical/lexical aspect of "large" is, I want to be able to search on Vinted for something that fits, and not have to check every time whether they really mean (for example) size 12 or they really mean size Large, which come together in the search, and then also have to include size 10/M in the search just to find size Mediums, but then have to sift through tons of things that are properly size 10s. Most people here have replied that for them, wearing size 12 tends to mean they also choose Medium, and that's what they'd like Vinted to group together.
But I guess this gives a chance for people to bring out the usual cliches about vanity sizing, how people don't know how big they are, how fat everyone is nowadays, how the average size is way too high, how everyone in the past was nice and slim, how tiny they are themselves, how much slimmer other countries are etc etc. Yeah we know all that, it's repeated here often enough. But the point here is about which sizes go together from numbers and letters, and how Vinted has possibly got it wrong.