In Italian, when I am talking about an unknown person, I would use the third person singular, masculine. For example, I could say Chi ha rubato le chiavi alla ragazza è qualcuno che ha potuto avvicinarsi alla ragazza (literally, "he who has stolen the girl's keys is somebody who has been able to approach the girl"); if I would use the feminine gender, I would imply I am talking of a woman/girl. In this case, the sentence would not use qualcuno, but qualcuna.
Is using he as a neutral gender acceptable in English?
A friend of mine said that she considers using he as a neutral pronoun acceptable, but I have noticed that (for example) some error messages given from applications, or web sites use the singular they.