Em dashes don't nest (but that's probably a good thing).
That is a weakness of sorts, but yes, unless one is attempting a particular, niche affect, an urge to nest parenthesis is usually a cue to re-write the sentence instead.
That is a weakness of sorts, but yes, unless one is attempting a particular, niche affect, an urge to nest parenthesis is usually a cue to re-write the sentence instead.