The point is not really whether it's intuitive or not (and for very nested expression, it's really not always intuitive to find the most nested one, especially

The point is not really whether it's intuitive or not (and for very nested expression, it's really not always intuitive to find the most nested one, especially if you have to remember precedence laws). The point is that it takes time. As much of an RPN fan I am, I am not convinced that the time it takes my brain to identify nested expressions is smaller than the time it would take me to just type the expression left to right on a regular calculator.