Technically yes. In practice: not advisable.
Three reasons
An ordinary household washing machine cannot process a good down duvet as it should. Three reasons.
One: a duvet is large. A seven- or nine-kilo machine has not the room to let the duvet move during washing. Water does not reach deep into the filling. What remains is a duvet that smells of detergent on the outside but is not clean within.
Two: the drying is rarely complete. A duvet must dry for hours at a low temperature. A household dryer can usually not deliver that. A duvet not fully dried develops mould in the filling. Sometimes visible, more often felt only months later, when the duvet stays clammy or smells.
Three: high temperatures or vigorous programmes can attack the natural oils in the down. After that it loses its loft, its warmth, its working.
What we do allow
What we do allow: a duvet in an industrial machine of a specialist atelier, with the right detergents and the right drying cycle. That is what we do here.