Watching two people argue about serial commas is like watching two people argue about politics: Neither can listen to the other, but neither is necessarily right nor wrong.
As a refresher, the serial comma—sometimes called the Oxford comma—is used in a series as in ham, eggs, and toast. It’s the comma after the word “eggs.” Without the serial comma, it looks like ham, eggs and toast.
Whether or not it is used depends on the style you’re following. For example, I usually default to AP style, which does not require a serial comma, but you might be a serial comma believer. It’s okay. We won’t argue about it, I promise! You’re not wrong! Just different.
There is one difference, however, that I do think makes the non-serial comma users wrong: Defaulting to rules over readers. Just because the rule is not to use that last comma, that doesn’t mean you’re writing clearly if you leave it out. Consider this sentence I came across recently:
In fairness, it probably is true that physical touchpoints are more important — in the retail, food and beverage and packaged goods fields that dominate the sample.
Without a serial comma after the word “beverage,” this sentence gets confusing. Is it food and beverage? Beverage and packaged goods? Wait, is it food and beverage and packaged goods? Is that a thing?!
Needless to say, I had to read it twice. And that’s going against the reader. When we make the reader work to understand our writing, we’ve failed the reader, and ourselves, because we haven’t communicated as clearly as we could have.
This is especially true today when everyone is scanning, going so fast that they might just misinterpret what you’ve written if you’re not crystal clear. (Or they might skip what you wrote altogether if you make them work to understand it!)
Will it make you a better, faster writer if you have to stop and think about whether or not to include a comma, or in any other way disobey a rule for the sake of a reader? Yes, because you’ll err on the side of communicating over correctness.
Rules exist to help us be consistent writers. But readers must come before rules.