The thing is, words borrowed from other languages are now part of your own, and you shouldn't have to know the grammar of each and every of these languages to use these words!
I
know that octopus is octopodes in plural, and platypus is platypodes, because that's the way it is in my language. But when I speak in english, it doesn't feel right. I too might say octopi or platypi. And as I said before, it makes sense because I handle it as an english word (and english handles it as a pseudo-latin), and it's not the first greek word that's used differently in english.
Take 'chaos' for example. Want to start pronouncing it Hah-os? Because that's the correct pronunciation
