Is it possible not to know your native language?
Man, just like that, no, it's not. But to post in the Spanish section you don't have to have Spanish as your native language. Maybe you were born in another country and went to a Spanish-speaking country to live 10 years ago, which would also explain some imperfections in your writing.
Although I think it is quite clear that in the case of Zerato and N.O. they are two non-native users who are using local forums to rank up, and using translation tools.