They overlap as you overlap leading to a kind of romantic mountain duvet.
Hmmmm, well I kinda look at it as a form of Polish birth control, this large "mountain duvet" between you and your significant other is not exactly conducive to intimacy.
What do people do in other countries? Lie on one sheet and cover themselves with another?
Bingo! Yes, that's how beds work everywhere I've been.
Come on, make up your mind, are sheets used in Poland or not?
Yes they are, but only to cover the mattress, never between the occupant and the duvet.
And one more thing I love about Polish beds, is this idea of refering to any bed large enough for 2 people as a "marital bed"