The edge nobody notices can still be the edge that cuts someone.

Harm does not require intention or even awareness. A sharp corner at the height of a child’s face, a step that is invisible in low light, a form that assumes everyone has a fixed address: none of these were designed to hurt anybody, and all of them will. The people who built them genuinely did not see it, usually because they were never going to encounter it themselves. Not noticing is the mechanism, not an excuse.

When somebody tells you they got caught on something you cannot see, believe the report before you interrogate it. Then go and look at the edge.