Why would a translator leave comments all over the translation?

Question

The book Slapping the Table in Amazement: A Ming Dynasty Story Collection is:

[...] the unabridged English translation of the famous story collection Pai'an jingqi by Ling Mengchu (1580–1644), originally published in 1628. The forty lively stories gathered here present a broad picture of traditional Chinese society and include characters from all social levels. We learn of their joys and sorrows, their views about life and death, and their visions of the underworld and the supernatural.

The introduction contains the following:

TRANSLATORS' NOTE

This translation follows the text of the 1628 Shangyou Tang edition of Pai'an jingqi as repreinted in the 1986 facsimile edition published by Shanghai Guji Chubanse. In this translation, the interlinear comments (IC) and marginal comments (MC) in the original text, often difficult to read, appear in italic within parentheses in roman text and in roman with parentheses in italic text.

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Here's an example of one paragraph with the MC and IC comments that are riddled throughout the text:

Stomping his foot, Mr. Jin said, “Those ingots of silver are my life savings. I also had a dream last night, and when I woke up, they’d vanished. I heard your name and address in my dream, which is how I found my way here. So this must have been the will of Heaven. This old man has no complaints (IC: Complaints wouldn’t do any good.), but I do wish to have a look at them, so that I can relieve myself of this weight on my mind.” (MC: As foolish as ever.)

Comments left as footnotes I could understand but what purpose does this type of comments have left all throughout the translation?

Answer 1

If I understand correctly, the comments are in the original text. That's what the translator's note says:

the interlinear comments (IC) and marginal comments (MC) in the original text

If something is in the original text, the translator has to translate it. What the translator did is adapt the format to what we're better used to nowadays, and what is easier to print: instead of the comments being on the margins or between lines, they are placed within the text. Such formatting is within the translator's purview.