Whatever happens, I won’t tell anybody about it.
Original sentence: Quoi qu’il se passe, j’en parlerai à personne.
Should this be: Quoi qu’il se passe, je n’en parlerai à personne.
(with “ne“ in front of “en parlerai“)
Or is it ok to leave that out and a French speaker would know what you meant?
Technically, this would be the grammatically “correct” version,
and I would use it in writing.
Would you be understood if you said: “J’en parlerai à personne.” ?
Definitely ! In fact, I would say that’s most people’s default, when speaking.
(On a side note: “Quoi qu’il se passe” is the literal translation of “Whatever happens”, but I think “Quoi qu’il arrive”, is much more common in French.)