Beginner : Use of comma in some short simple question - answer dialogue

Question

здравствуйте, hello,

I'm following a Russian language course for beginners (for I am one) on Youtube [1].

Here is some example dialog about interrogative words and negation :

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Чьё это пальто ? Я не знаю , чьё это пальто .

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My problem :

This use of the comma seems very odd to me, and I'm wondering whether I should learn it as a syntax / punctuation rule for the use of commas in the Russian language.

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In French, my mother tongue, I would say

À qui est cette veste ? Je ne sais pas à qui est cette veste.

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In English, I am not completely certain but this :

Whose coat is this ? I don't know whose coat this is.

sounds much better than :

Whose coat is this ? I don't know, whose coat this is.

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My reasoning :

For me it seems logical not to have the comma because the part "чьё это пальто." in the answer is the "direct object" of the action "Я не знаю", as I understand it in French and English.

I know Russian sometimes constructs sentences in a much different way, so any advice, short or long, will be much appreciated !

Thank you in advance, and of course please feel free to correct me on my English sentence if it's wrong. And for my use of commas in general ^_^ .

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Notes: [1] Full Russian language course for English speakers produced years ago on videotapes and archived by some American language school. Question for moderators : should I provide a link or would it be advertisement ?

Answer 1

This comma is really needed, and it's absolutely in full consent with the Russian grammar.

The rule is: "every clause that has its own subject and predicate is to be sparated with commas." {rule 1}

In Я не знаю, чьё это пальто. there's an objectibe clause чьё это пальто, inside it это пальто is the subject and чьё is the predicate, so, according to {rule 1} it has to be sparated with commas.