I have a similar rule when writing documentation. As soon as I find myself writing something in the passive voice, I know I’ve hit part of the system I don’t really understand. “This event happens” instead of “subsystem A triggers this event”.

Nitpick: “This event happens” is not in the passive voice. “This event is triggered” is in the passive voice — and so is “this event is triggered by subsystem A”. (What you probably mean is “writing something vague or lacking agency”.)