What irritates you the most with your own language?
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"
My language is diglossic - it has a written form and a spoken form that are very different to each other. It's quite difficult to understand the written form if you've only grown up speaking and listening to the language, as the written form is essentially the language as spoken in the 1600s.
To compare it to English, it would be like saying "Where are you?" to someone over the phone, but then having to send them "Wherefore art thou?" as a text.