Punctuation ain't grammar

The Harris and Walz nominations have generated a flurry of back-and-forth arguments online, not about their political views, but rather how to make their names plural and possessive. 

Here is orthodoxy:

Singular: Harris, Walz

Singlar possessive: Harris's, Walz's

Plural: Harrises, Walzes

Plural possessive: Harrises', Walzes'

Punctuation is a matter of convention, not grammar. In the eighteenth century, for example, it was common to put a comma between the subject and verb of a sentence, but we no longer do that. And it is not unusual for different conventions to continue in use. 

For example, Associated Press style advises that because Harris is a proper noun, Harris' is an appropriate singular possessive. In its majestic inconsistency, the AP also advises that common nouns should take the 's, viz., boss's. *

One long-standing tradition is to make classical and biblical names possessive with the apostrophe: Socrates', Jesus', but the Chicago Manual of Style advises to use 's. If Jesus's makes you twitch, do not use it. 

Some people assert that words ending in z should be made possessive with an apostrophe only. You do you. 

Some people use 's to make names plural: the Smith's. That is right out. People will know you were not paying attention in English class. 

If you are writing for a publication that has a house style on punctuation, follow it. If you are writing for a publication that does not have a house style on punctuation, may God have mercy on your soul. If you are writing for yourself, pick a style, follow it consistently, and stop arguing with people online about which style is right. 

* The Associated Press is responsible for many quirks in journalistic writing. Newspaper reporters overuse the em dash (—) to set off parenthetical material rather than parentheses, because they use parentheses instead of square brackets to set off information added to quoted material. The AP doesn't use square brackets ([ ]) because it cannot transmit that punctuation to all the clients. That is also why AP uses quotation marks for titles and other material rather than italics. Keep in mind that when you shift from a book to a newspaper, you are code-switching punctuation.