enhanceur /ˌɒnhɒnˈsɜː(r)/ noun

Etymology: Early 21st century: from French, blend of enhance + -eur (agent suffix), modeled after saboteur. First documented usage in online forums discussing "reverse vandalism" and "guerrilla kindness."

Definition:

A person who secretly improves public spaces, systems, or situations without seeking recognition, often leaving others pleasantly confused about why things work better than expected.

(informal) One who commits acts of clandestine betterment; a benevolent phantom who strikes when nobody is watching.

Example sentences:

"The office enhanceur had struck again—someone had mysteriously fixed the perpetually jammed printer, replaced the dried-up pens with working ones, and nobody had seen a thing."

"After years of finding public toilets inexplicably cleaner than expected, Marcus began to suspect the existence of a secret society of bathroom enhanceurs."

"The park's enhanceur worked only at night, planting flowers in bare patches and repainting faded benches, leaving morning joggers to wonder if they'd imagined the previous decay."

Usage note: Unlike their destructive counterparts (saboteurs), enhanceurs suffer from a peculiar occupational hazard: nobody believes they exist. This has led to the common phrase "enhanceur's paradox"—the better you are at your job, the less evidence there is that you were ever needed.

See also: ninja janitor, guerrilla gardener, phantom fixer, anonymous benefactor