The censor’s black bar can make the concealed detail become the center of attention.

Concealment marks a location. The bar tells you exactly where the interesting thing is, and attention goes straight to it, so the act of hiding produces the focus it was meant to prevent. Redaction advertises.

This is worth knowing when you try to keep something from being noticed. The visible gap, the topic conspicuously not mentioned, the person carefully not named, all draw more attention than the thing would have. If you need something to pass unremarked, hiding it obviously is the least effective method available.