NOTATIO

I'm curious about the use of a bracket...
wouldn't that sort of clutter a score? (I'm thinking, for example, of a large orchestral score.)

I've used brackets a few times in passages that were rhythmically ambiguous, but only for a few instruments.

You could always hide them in the score.

As far as I can recall, Arnstein only used brackets in parts.

ahh, yes, that would make a difference.