I have been grappling with the question below for a while now, so hope that you can shed some light on it.
Do we need the first comma (the one in brackets below) in the restrictive nested subordinate clause (adverbial, noun and relative clauses -- all 3) that is embedded right into another restrictive subordinate clause after a subordinating conjunction and if yes, could you please explain why?
See example sentences below (please ignore the actual sentences; I just want to understand the logic of the punctuation for the 3 types of nested subordinate clauses - so for the sake of argument, recasting or modifying these sentences is not an option):
1) This is the country where[,] if you work hard, you get rewarded. (relative clause)
2) We need to talk because[,] if we don't, we will be in trouble. (adverbial clause)
3) London is where[,] when I was young, I used to live. (noun clause)
4) Give me a call if[,] when you are at the station, it rains. (adverbial clause)
5) It is useful when[,] if it rains, you have an umbrella. (awkward adverbial clause)
6) She is the person who[,] if she is faced with difficulties, can handle them very well. (relative clause)
7) He said that[,] if all goes well, he will call. (noun clause)
The thinking here is that the first (bracketed) comma should be dropped as the embedded subordinate clause is restrictive / essential to the meaning of the main subordinate clause (e.g. in the first sentence, for instance, you only get rewarded if you work hard) and in this case treated as an introductory clause to the main subordinate clause with one following but not preceding comma (just as if the main subordinate clause was in the beginning of the sentence before the independent main clause).
If the comma is retained, however, the embedded subordinate clause is read as parenthetical / non-restrictive clause, which, for the sake of these sentences, is not intended (the clauses are intended to be restrictive on purpose).
The partial confusion lies in the fact that some style guides like Chicago Manual of Style 16th edition in 6.32 says in the cases like this:
6.32 “And if,” “that if,” and the like When two conjunctions appear next to each other (e.g., and if, but if), they need not be separated by a comma.
They decided that if it rained, they would reschedule the game.
At the same time, many of subordinating conjunctions in the embedded subordinate clause are also relative adverbs or pronouns and fulfil either an object or subject roles in the main subordinate clause, which then makes the embedded subordinate clause interrupt object / complement - subject (sentence 1 and 3) and subject - predicate (sentence 6) relationship in the main subordinate clause, requiring commas on both ends (just as if the main subordinate clause was inserted between a subject and verb, or verb and object of the independent main clause) - in which case it conflicts with introductory clause logic and CMOS guideline above (actually, do subordinating conjunctions in sentences 2, 3 and 5 have adverbial functions, in which case the embedded subordinate clause acts as interrupter as well, in which case commas, again, are required on both ends?).
Hope this makes sense - any thoughts are greatly appreciated.
I am not really after how to punctuate these exact sentences - more just to understand the logic of punctuation (and especially, if it conflicts like sentence 7 that is similar to CMOS example vs other sentences)
Also, would be good to understand if different embedded subordinate clauses are treated differently depending on their relationship to the main subordinate clause.