I am confused whether comma is required after adverbial (dependent) clauses at the end of the sentence (and the difference, if any, between restrictive and non-restrictive adverbial clauses).
The internet and various style manuals seem to give conflicting advice, so I am not sure what is true or, at least, what is prevalent.
According to Purdue University (Purdue Owl), no comma is needed, except cases on contrast, when dependent clause follows independent clause, presumably because they are all treated as restrictive.
She was late for class because her alarm clock was broken.
Yet Gregg Reference Manual, 10th Edition and CMOS 16th edition both state that comma is required if the dependent clause following an independent clause is non-restrictive in meaning, but no comma is required if the clause is restrictive.
Gregg gives the following examples of restrictive and non-restrictive dependent clauses (dependent clauses in italics - notice the comma in the second example):
Restrictive: His faxed response came after you left last evening.
Non-restrictive: His faxed response came this morning, after the decision had been made.
While I see the logic and the difference, I would argue that the second example is also restrictive depending on what is being restricted. And, arguably, Purdue Owl would punctuate the second sentence, based on the advice given, without the comma.
So what holds true here?
Is there a majority-accepted rule (or, at least, majority position) around restrictive / non-restrictive adverbial clauses, or is this merely a stylistic / subjective preference? Could all clauses be punctuated as restrictive, aside from some obvious exceptions below?
I know there are some exceptions with negatives clauses (Not because, but because, etc.). And also when the clause is clearly an afterthought (I can do this, if you wish). But in cases like the above where either interpretation is possible what is the prevalent editorial position?
Could I argue that the sentences below should also be punctuated without comma on the ground of stylistic / subjective preference - rationale in brackets?
I will see you at 9.35 pm after the party has finished. ("9.35" describes what time; "after the party has finished" describes circumstances - both restrictive; no comma.)
The plane landed after 10-hour flight at 10 am. ("after 10-hour flight" describes circumstances; "10 am" describes time - both restrictive; no comma.)
Thanks a lot in advance (editing a piece of work and cannot go to sleep as these adverbial constructions keep coming up).