Two in the bed with different temperatures
Short answer: Use two single duvets rather than one double. It is the only solution that lets each of you choose your own weight without compromise.
Why a shared duvet does not work
Two adults give off different amounts of heat and have different comfort zones. A shared duvet can only sit at one point on the scale, and then one of you is cold or the other sweats all night.
The two duvet solution
Two single duvets in a double bed let each person choose their own weight. It also solves the problem of one person pulling the duvet across. See bamboo bedding.
The sheet underneath
A shared sheet is still fine. A bamboo sheet carries heat away from the skin and helps the warmer of you without bothering the other. See bamboo sheets and bamboo fitted sheets.
Frequently asked questions
Do two duvets look untidy
Not if they are the same colour and laid out neatly.
What size is a single duvet
One hundred and forty by two hundred centimetres is the usual Danish size.
Can you have two different covers
Yes, but it is easier to keep track if they match.