This isn't FB, so here, we can state our opinions or experiences on subjects like this, unless we wish to provide proof to back up what we're asserting.
For our silkies, even frizzled and molting (skin exposed), we've kept our coops at 40°F for a decade—using an oil-filled radiant heater in the smaller coop and a non-digital electric heater installed in a wall of the large one. Four growout pens have Cozy Coop radiant heaters. It was -11F with -35F wind chills two days ago, and it will get much worse before winter is over.
Everyone was fine. Proof of that is they lay all winter, although about half as much.
If we had just a day or two of below 32°F in our insulated, dry, draft-free coops, I wouldn't worry. It's when it goes on for several days/weeks, it's common sense that it would wear on the chickens constantly having to keep themselves warm. A little supplemental heat makes them more comfortable.
Another very important reason the coops get heated is for me! I'm old, and I refuse to trudge through snow to bring out water twice a day or deal with frozen eggs. If I had to do that, we wouldn't have chickens.