CMBS fired on a completely straight clear stretch of highway - sunny day, no obstructions, no debris, no cars visible in front, nothing. Slammed on the brakes and dropped me 25 mph from highway speeds before I could recover the car. I was thrown forward into the seatbelt, and if there'd been anyone behind me it absolutely would have caused a collision.

Happened 3 times in 60 miles before I pulled over to figure out how to disable the thing - turns out, there's no way to do so permanently, you have to remember to disable it every time you start the car (or roll the dice and drive with randomly-crash-my-car mode enabled).

Update from Feb 1, 2022 Update: After having the car examined by a Honda service center, they let me know that the sensor was "performing to spec" - this wasn't a fault sensor, Honda just expects that its Honda Sensing system will sometimes brake check at maximum braking without warning (the dealership page about the system even says that this situation is "not uncommon"). I have no idea why the NHTSA hasn't forced a recall.