[cryptonector]

I think you're quite right that mixing different separator uses of the same punctuation character is a source of ambiguity. This is where em-dashes and parentheticals shine.

It's also a good idea to rephrase to avoid the ambiguity. E.g.,

    To my mother, Ayn Rand; and also to my daughter, and God.

or

    To my mother, to Ayn Rand, to my daughter, and to God.

It's not always possible to just sprinkle a comma to disambiguate, so don't just do that. Use other punctuation. Add punctuation diversity to your writing -- make it clearer and more fun for you to write, and others to read.

The trick is to notice these issues as you write. Of course, that's not always easy, and it's particularly difficult when speaking, but at least it's not usually expected when speaking.

[vidarh]

When speaking, we will also often address it by changing intonation and shortening pauses to indicate that we're interjecting something rather than continuing a list. E.g. in this case adding pressure to "Ayn Rand" and shortening or cutting the pause implied by the first comma if we want to imply they're one and the same:

To my mother Ayn Rand, my daughter, and God.

And if we sense ambiguity we'll often similarly extend subsequent pauses to clearly separate list items.

We'll also often add body language to make the emphasis on connections even stronger.

I'm guessing a lot of ambiguous written lists are ambiguous because people have written the words roughly how they'd said them, and tried to follow grammar rules without thinking about the extra cues they're leaving out that'd be there if speaking.