Ours isn’t 8kg and I couldn’t fit a decent thickness duvet in it. If it were a thinner summer weight one and only a double then maybe, but our king size and double 13.5 Tog duvets won’t fit in it. I’d need about a 10kg capacity and even then it would probably be a squeeze.
For anyone looking, for a machine that will take a duvet. Have a look at the drum volume above the weight rating of the machine .
The grading for weight capacities are a bit of a con. When they’re being graded, manufacturers can have the clothing professionally folded -stacked top to bottom and front to back they can also use the door boot (rubber bit); and worst of all, the door OPEN! So basically they can use every inch of drum space, in a way that would never work for actually washing clothes.
You can find machines with the supposed same capacity in weight, but they’re totally different volumes. Eg, Hoover/Candy machines tend to have tall and shallow drums, which would never fit a duvet and then others like Bosch will have short and deep depth drums that will take a duvet.