> "To my mother, Ayn Rand and my daughter"

- Ayn Rand can't be in apposition of my mother as there's no comma setting Ayn Rand off from my daughter

- Similarly, Ayn Rand and my daughter are not in apposition

- my daughter and my mother are mutually exclusive

This is described in more detail here:

https://en.wikipedia.org/wiki/Serial_comma#Ambiguity

> "To my mother, Ayn Rand, and my daughter"

Adding the Oxford comma creates ambiguity between my mother and Ayn Rand, unless the speaker is Ayn Rand's daughter.

But here we're using semantics to disambiguate. It works, sure, but it works in fewer cases than punctuating/rephrasing to avoid the ambiguity grammatically rather than semantically.

Semantic disambiguation also imposes a higher cognitive load on the reader -- sometimes that's the point (high-brow writin'). But you should consider the poor reader. After all, you want to be read and understood.

Sure, which is why I mentioned the exception. The whole point of the example is to show there are cases where the Oxford comma alone doesn’t prevent ambiguity in all cases. I’m not arguing that the Oxford comma is silly. I’m just explaining how the example can be ambiguous. Language is messy and wonderful and frustrating and fun!

It only says the mother is Ayn Rand if the comma after mother is taken as making an appositive phrase. There is no later comma to end the appositive phrase, so we'd have to take "Ayn Rand and my daughter" and so it would be saying that his mother is both Ayn Rand and his daughter.

That's not possible so we can rule out the comma making an appositive phrase, and see that it must be a list comma, and we've got no ambiguity.

Putting in the Oxford comma makes it so we could interpret "My mother, Ayn Rand," as an appositive phrase, and we have ambiguity.