Speaking only for myself, I have to say I actually find your point-free version of "sum" more readable. The extra argument is just visual clutter. Pointless st

Speaking only for myself, I have to say I actually find your point-free version of "sum" more readable. The extra argument is just visual clutter. Pointless style only gets really confusing when you end up with a bunch of composition operator sections shuffling the order of things around in unclear ways.