Can somebody help to clear up three issues I'm having with 'nonessential commas'.
Firstly, does this use of the comma only concern itself with modifiers, wether it be appositive phrases, adjectival clauses, etc., etc.? They cannot be used to set aside other sentence elements?
Secondly, why can full clauses--clauses which could stand as their own sentences-- be enclosed in dashes and parentheses but not commas? Commas, dashes, and parentheses all function in the same way when 'setting aside parenthetical elements', aren't they? It would just become a simple splice with commas, no?
And, finally, how can a nonessential aside have its own internal aside within one sentence? I'm talking specifically about commas here; I'm not talking about, for example, a non-essential relative clause that contains further context in parentheses or dashes. Here's an example sentence I've just made up: "Jack opened the can with ferocity, which surprised his mother, who herself felt the same rage within herself." This is a terrible example (I've had a long day), but I come across sentences of this form all the time. There's even sentences that contain a parenthetical within a parenthetical, within yet another parenthetical. What's the deal?