Mine is people who separate words when they write. I'm Norwegian, and we can string together words indefinetly to make a new word. The never ending word may not make any sense, but it is gramatically correct

Still, people write words the wrong way by separating them.

Examples:

• "Ananas ringer" means "the pineapple is calling" when written the wrong way. The correct way is "ananasringer" and it means "pineapple rings" (from a tin).

• "Prinsesse pult i vinkel" means "a princess fucked at an angle". The correct way to write it is "prinsessepult i vinkel", and it means "an angeled princess desk" (a desk for children, obviously)

• "Koke bøker" means "to cook books". The correct way is "kokebøker" and means "cookbooks"

I see these kinds of mistakes everywhere!