Should indentation disambiguate additional arguments to function call vs a new expression?

[gwhitney]

Consider

[
   f a,
     b
]

vs.

[
   f a,
   b
]

They both translate to [f(a,b)]. (It may be quite too late in the design process but) is there an argument that continuing arguments to a function call should require some indentation? Certainly I always write it that way, and was in fact surprised that

[
   f a,
b
]

wasn't either a parse error or at least put the b as a second element to the array. To me it is very counterintuitive that a line with less indentation can be a continuation of one with more indentation -- it strongly conflicts with/messes with my visual scanning of the "profile" of the code on the screen.