Comment by ofalkaed

>It's not a choice you'd make today obviously, but it was entirely reasonable then.

More recently, BQN made this same choice and I think it is perfectly reasonable to do as long as you have a reason beyond simple aesthetics. Entering these symbols on a normal keyboard is not difficult and no different from learning a human language which uses a different alphabet than you keyboard.

Personally I find the custom symbols of APL and BQN to be easier to type and read than the ASCII of J and K.