Learn Italian: È un fenomeno strano, ma se ne discute frequentemente. - It is a strange phenomenon, but people discuss it frequently.

When the impersonal pronoun si (meaning "one" or "people") is placed directly before the pronoun ne, the si always changes to se. This creates the combined clitic cluster se ne.

The English translation is "discuss it". Why do we use ne instead of a direct object pronoun like lo?

In Italian, the verb is usually discutere di (to discuss about something). Because it requires the preposition di, you must use the pronoun ne (which replaces phrases starting with di) to mean "about it", rather than a direct object pronoun.

Could se ne discute be translated using the passive voice instead of "people discuss it"?

Yes, absolutely! The impersonal si construction is very often used in Italian where English would use the passive voice. Translating this as "it is discussed frequently" is completely natural and correct.

Since si (and se) can also be reflexive, how do we know this isn't a reflexive sentence?

It comes down to the verb and the context. While a cluster like se ne is used reflexively in pronominal verbs like andarsene (to leave), discutere isn't typically used reflexively. "He discusses it with himself" would be a very unusual interpretation here, so the impersonal meaning is the obvious choice.