Parenthetical commas

Question

Parenthetical/nonessential/non-restrictive commas are proving to be the bain of my life atm.

My first question is whether they are all names relating to the same idea? Non-restrictive modifiers, for instance, always describe either a noun or verb of the sentence, yet words that are interjected into the sentence are said to have no grammatical relation to anything else. When speaking in the vocative, as well, or enclosing apoosited dates/geographical locations, some style guides recommend treating these as parentheticals; however, they seem to be functioning differently from modifiers, no? Can these interruptions or asides be almost anything, so long as they are fragments and don't contain a subject-verb agreement?

Secondly, are introductory words, phrases, and clauses also considered nonessential modifiers/parentheticals when separated by a single comma? Sometimes they contain the important info. and then a pronoun steps in as the main clause's subject.

Is it acceptable to place any type of parenthetical at the end of the sentence? It's common to see nonessential appositives or non-restrictive modifiers following the main clause, but less common to see interjections, for instance.

finally, why is it acceptable to have one nonessential being nonessential to another nonessential, which itself might be acting this same way to the main clause, as in this sentence: The bike store included the later models, including the 9400x, which itself had state of the art tyres." The second dependent clause is functioning as a nonessential to the first nonessential, right? Could this pattern be repeated ad infinitum?

Apologies for the length, and thanks in advance for any responses.

Answer 1

It may be that distinguishing the mechanics of punctuation from the functionality of various sentence elements will ease your confusion. Commas set off various constructs from the rest of the sentence:

• Exclamations ("Oh, damn it all!")
• Vocatives, i.e., direct address. ("Watson, come here.")
• Appositives, i.e., renamings. ("I live in Albany, the capital of New York.")
• Non-restrictive or non-essential relative clauses. ("My sister, who lives in Albany, ....) Note that this tells you only incidental information about my sibling, while "My sister who lives in Albany" defines or restricts the discourse to this one sister as opposed to my other sister who lives in Trenton.
• Introductory subordinate clauses. ("While I was in Albany, I visited my sister.")
• Nominative absolutes. ("Having business in Albany, I decided to visit my sister.")
• Parentheticals or interruptions of the main body of the sentence. ("My dear, quite frankly, I don't give a damn.")

These aren't hard and fast rules. For example a closely-bound appositive won't take commas: "My sister Sue lives in Albany." And, of course, commas have other uses, such as separating conjoined independent clauses or separating items in a list.

The Chicago Manual of Style notes that "Parentheses, like commas and dashes, may be used to set off amplifying, explanatory, or digressive elements. With a "close logical relationship to the rest of the sentence," use commas; otherwise, use dashes of parentheses. (Emphasis mine of the characteristics of a parenthetical.) You'll have to decide whether the parenthetical is a mere aside:

Let's call it (for lack of a better word) an "episode."

or a more important amplification. In any case, parentheticals, as elements partially independent of the sentence containing them, may have their own structure (including relative clauses) and thus their own punctuation. Ad infinitum.