"Some people here recommend against tinning, as it makes the wire stiffer, but I believe that the solder flowing into the insulation strengthens the ends against breaking and fraying, and flattening the hook increases the surface contact area."

Tinning is not a good idea, for the same reason that crimped on fork, spade or ring terminals should never be soldered. The solder wicks up the cable, creating a flexable to non flexable junction, which is where the wire will break after some movement. Kind of the opposite to what you would think.
Flattening the tinned section is a good idea, but unless you can get it perfectly flat, you'll probably have less contact area then with untinned cable.