Grammatically Correct: The writer's essential guide to punctuation ...

Brackets []
People often interchange the words brackets and parentheses, but,
aside from some minor overlaps, these punctuation marks have quite
distinct uses.
Brackets have two primary functions:
• Identifying changes to quoted material
• Enclosing digressions within parentheses
IDENTIFYING CHANGES TO QUOTED MATERIAL
If you changed any of the text in a quoted passage and did not
indicate that you had done so, you would be guilty of misquoting.
You may, however, make minor changes provided you clearly attribute
them to yourself. The convention for identifying which words
are your own is to enclose them in square brackets. Some writers use
parentheses instead, which may be problematic because parentheses
serve other purposes. That is, if the original material contains any
parentheses of its own, readers would have a hard time distinguishing
the original author's digressions from your insertions. Brackets, in
contrast, are unambiguous.
Brackets may be applied to quotes derived from oral sources,
such as interviews or press conferences, as well as from printed
sources. They are actually more likely to be necessary in the former
case, because speakers tend to choose their words more casually
than writers, leading to a more frequent need for clarification.
There is no specific length limit on the text you put in brackets,
but it should usually be quite brief; it is, after all, an interruption
of someone else's words. If you want to make a lengthy clarification
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