I know that a comma doesn't have functions to link two sentences.
But what would your life be like if you had never learned a language ? Could you still have friends, get an education, or hold a job? Language is so fundamental to our experience, so deeply a part of being human, that it's hard to imagine life without it.

---
Language is so fundamental to our experience, so deeply a part of being human, that it's hard to imagine life without it.

1)
I think "so +adjective + article +noun" structure is so common.
But this sentence indicates "So + Adverb + article + Noun" structure.

Is this sentence right?

2)
And the two complements of the Be verb "is" are written down in a row with a comma, not a subordinate conjunction. I know that a comma doesn't have functions to link two sentences.

Is it right?

So please help me understand it!
Thanks!

Question

I know that a comma doesn't have functions to link two sentences.
But what would your life be like if you had never learned a language ? Could you still have friends, get an education, or hold a job? Language is so fundamental to our experience, so deeply a part of being human, that it's hard to imagine life without it.

---
Language is so fundamental to our experience, so deeply a part of being human, that it's hard to imagine life without it.

1)
I think "so +adjective + article +noun" structure is so common.
But this sentence indicates "So + Adverb + article + Noun" structure.

Is this sentence right?

2)
And the two complements of the Be verb "is" are written down in a row with a comma, not a subordinate conjunction. I know that a comma doesn't have functions to link two sentences.

Is it right?

So please help me understand it!
Thanks!

Answer

1. Yes, the sentence is correct. It is perfectly okay to use "so" with an adverbial phrase.

2. The comma is there to separate "so deeply a part of being human" because it is an additional clause that is not necessary for the sentence. With that portion removed, the sentence would be written:

Language is so fundamental to our experience that it's hard to imagine life without it.

In that sentence, "that" is the conjunction. You could also write it this way:

Language is so fundamental to our experience, and it's hard to imagine life without it.

"That" doesn't take a comma, but it is still a conjunction. In fact, commas preceding conjunctions are mostly a choice made by the writer. The general rule to follow is that you should use a comma when the sentence is long, but it's up to you to decide when a sentence is "long enough" to warrant a comma.