What do you lose when you translate a footnote?

I was translating a passage where the author cited a 17th-century pamphlet in Latin, and the footnote said 'as if to say: this is not truth, but a performance of truth.' I kept that phrase, but it felt like a lie. The original footnotes—those little margins of confession—were never meant to be read as footnotes at all. They were confessions. Now they’re just annotations. What did we trade for clarity? And why does it feel like a theft?