"the couple left three devices on their sofa, all plugged in and charging for the following day...
Nothing which is being charged should be left on a heat insulating surface which is itself flammable. The draining board next to your kitchen sink is a much safer place."
Aside from 2 laptops which are pretty much permanently plugged in (but since their batteries are already charged, they'll just be drawing what they need rather than charging over night), I wouldn't dream of leaving anything to charge overnight. It's just not worth the risk.
My phone quick charges in under an hour from almost empty. There's no reason to charge it overnight, when I could instead charge it at my desk, or while I'm eating, or whatever.
Unlike my RC Car's high capacity batteries, which come with warnings all over them about proper charging care, not leaving them unattended, no common consumer product I have purchased in the last decade+ has come with any kind of visible warning regarding charging habits.
Common Sense over the last decade or two has shifted towards charging at night so your devices function all day.
Charging your phone fast is also bad for the battery in terms of heat production.