Why it matters when you are writing
The blanket advice to avoid it is bad advice. Choose the passive when the actor is unknown, irrelevant, or obvious; when the object is the topic your paragraph is tracking; or when the convention of your field expects it, as in the methods sections of most experimental journals. Style guides that ban it outright produce awkward sentences full of invented actors.
The real cost is agent deletion. “Errors were made in the coding” names nobody, and in a limitations section that vagueness is doing work you probably do not want. Where accountability matters — who decided, who coded, who chose the threshold — the active voice answers a question the passive leaves open, and reviewers notice which one you picked.
Field norms are shifting and it is worth checking rather than assuming. APA explicitly encourages first-person active constructions for your own actions: “we recruited 240 participants” is now standard in psychology. Many biomedical journals still prefer the passive throughout the methods. Read three recent papers in your target journal and follow what they do.