In reply to pancakeandchips:
Agree it's interesting. I do remember a book on rope technique (1970s) by Bill March which recommended, presumably for better braking, using just the smaller hole of an 8 in a similar manner to the slot on a a Sticht plate (no ATCs then of course). That would lead one to think the normal method of use was thought inferior for belaying. Of course there have been many different 8 devices which must each have different properties. I've seen various people using 8s to belay.....IIRC last time at Dancing Ledge where a group of kids was being supervised top roping (I think a second person was belaying the "inactive" rope after the first for safety).
I imagine paying out slack etc is easier with an ATC. Quite often people used to routinely carry an 8 for abseiling but took a tube device for belaying...I asked one and they said they felt abseiling with it was safer.