If someone is born in the Netherlands every middle name is a hard error, because the dutch law don´t know the term middle name.
It could be me, but middle names are only used in a very small part of the world, so maybe there should be a check on a location and if it is in that very small part of the world the middle name should be a hard error. Personally I don´t want to see the middle name, because to many people use it and I spend too many hours correcting and moving first names. If you see Jeroen Willem Van Van Dijk. Then that is an merging error. But Mary Ann Ann Smith is also very likely a mistake.