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"
In general I think Spanish is a well formed language without (or at least not much) crazy shit.
But I still don't know why we have the same fucking word for weather and time. While using the same word for different meanings is ok, these two are ridiculously common concepts used a lot and it's not hard to get into situations where it's hard to know which is which. Absolutely stupid.
As a Spaniard with kids living in UK, it's very hard to teach them the gender of words that should not really need to have a gender. Why does "car" need to be masculine?!
It's easier if you don't think it as actual gender, and just as grammar. You have "el televisor" (masculine) and "la tele" o "la tv" (femenine), both meaning "the tv". It's more about how the word ends than anything.
Still, it's something that if someone gets it wrong, it sounds off but everyone still understands. No one is going to care for a foreigner saying that wrong. There's no really a confusion to be had there.
But time/weather can lead to actual misunderstandings.
it's less of a Spanish thing and more of a cultural slang thing that is really not more of an issue than any other slang in any language can create, which is to say, rather minor.