Huh? You think they're literally editing radio broadcasts, network transmissions, printed media, etc? And that nobody has noticed? I think your tinfoil is leaking!
I more meant they could be editing transmissions and inputs from all the digitally-based means we have analysing the universe - including Voyager, telescopes, gravity wave detectors... CERN.
It was an idea I pondered trying to turn into a short story, but I'm not a writer, so.. here we are.
https://ia801004.us.archive.org/0/items/truenamesvingevernor...
His later book A Deepness in the Sky also revolves around the same ideas.
An excellent, highly scalable (and scaled) way of not being able to notice things.