Question

How can comma placement change the meaning of a sentence?

Answer 1

Commas can alter the meaning by modifying the grouping of words.

Explanation:

Here is one example:
[1]`color(white)("XXX")`I saw the twins, Alice and Josie.
versus
[2]`color(white)("XXX")`I saw the twins, Alice`color(red),` and Josie.

In case [1] I saw two people, namely the twins whose names were Alice and Josie.

In case [2] I saw four people, namely the twins and also Alice and Josie.