False Negative

A false negative is when a moderation system fails to flag content that was actually harmful. The system said "fine" when the correct answer was "harmful." It is the error that leaves victims unprotected.

What it means

False negatives are the harm that slips through. They happen when abuse is worded cleverly, disguised with misspellings or code, or expressed through subtext that a shallow filter never learned. A system tuned to avoid ever bothering innocent users will let more real abuse pass, so false negatives and false positives trade off against each other.

Real-world examples

• A coded threat that avoids every banned keyword and is not caught.
• A slur disguised with symbols or deliberate misspelling that a blocklist misses.
• An indirect encouragement of self-harm that a literal filter reads as harmless.

Why it matters

Every false negative is a piece of real harm that reached its target. Too many of them mean the moderation system is not actually protecting the community, no matter how quiet the logs look. Catching the subtle cases is exactly where implicit moderation matters most, because the abuse that evades detection is rarely the obvious kind. Measuring false negatives is done through recall, one half of precision and recall.