The "De" in this name should never drop, even when dropping of "non-dropping" particles is forced.
I'd like to return to this issue since, just like aurimas, I feel the current implementation is markedly problematic:
Hence I’d like to repeat aurimas’ and my suggestion:
My favourite is what I see as the cleanest solution: introducing additional fields for dropping-particle, non-dropping-particle and suffix, by adding a "five-field" state to the name field (in addition to the existing "single field" and "two-field" states).
An in-field markup syntax would also be possible, e.g., by using something like the pipe character ("|") to separate subfields inside lastname and firstname fields.
Unfortunately, I cannot code any of these but I’d certainly be willing to contribute to testing.