Read a Mike Shepherd novel, Kris Longknife: Mutineer.
Here’s a passage in the novel:
I hate having to double read a sentence and this just required it.
No one said, “Yes sirs.”
Two people said, “Yes sir.”
Should it have been written:
"Yes sir"s answered him.
Oh and by the way, if more than one person can fit into a captain’s day cabin then they have to be very good friends.
Never mind
An apostrophe isn’t correct, but for some reason, “Yes sir’s” reads more clearly to me than “Yes sirs”. “Yes sirs” sounds like someone is saying “yes” to more than one sir.
"Yes sir"s looks wrong.
I feel sorry for writers. 
ETA: I’m not sure that quotation marks are even necessary in this example.
I agree with Auntie Pam. If I wrote that, I would have either said, Yes sirs answered him. Or “Yes sir.” replied character 1 and character 2.
Although I am not particularly found of the answered him. It seems to add confusion as to who is responding.
How about something like:
a chorus of yes sirs
That’s hard to see… the “yes sir” italicized and the “s” not. Maybe it wouldn’t work.
It does, doesn’t it.
Yet that there ‘s’ just does not belong within the quotes.
It was not part of the dialog.
We need a seance for Papa Hemingway’s opinion.
I’ll get my Ouija board.
In the meantime, Mr. Shepherd should be ashamed of himself for writing such a clumsy sentence.
Nevermind the quotes issue, “answered” is a transitive verb in this usage and gives “Yes Sirs” a personification that feels really odd.
Sometimes you just can’t make the sentence work as you first imagined it, and rewording is necessary. This is one of those sentences.
Isn’t that four people that said “Yes sir”? I would have written it like this:
“Yes sir!” said Addison.
“Yes sir!” simultaneously from Longknife.
“Yes sir!” came from the XO.
Not to be outdone, a resounding “Yes sir!” was snapped out by the Comm officer.
Yes sir.
By the way, liked your alternative.
"Yes sir"s
is correct.
But it’s a very poor sentence and his editor should have tasked him about it.
Nitpick:
Should be anthropomorphism.
A personification is a person; an anthropomorphism is a non-person given the metaphorical characteristics of a person.
Totally invalid definition, IMO. I think I see where you get it from, but you’re wrong.
A personification is the metaphorical giving of personal characteristics to an entity which is not normally regarded as having a personal identity. “O West Wind, why dost thou blow?” “The wrath of the Democratic Party…”
An anthropomorphism is the attribution of human characteristics to an entity (real or imagined) which is objectively not human. “The cat eyed her skeptically but granting a purely temporary tolerance.” “Pele’s fiery wrath masked her bounty in the rich crops grown in soil fresh-ground from her gift of lava.” Deities, animals, and occasionally plants and discrete inorganic objects may be regarded as having human characters.
There’s a slight overlap but a really significant difference. Only in cases where “personification” is used synonymously with “epitome” is a ‘personification’ actually a person. “Gadsby is the personification of conspicuous excess.”
Those are excellent examples of anthropomorphisms, or less correctly, but still usage-wise widely accepted, personifications.
I agree that incorrect usage has blurred the lines, but I will continue to fight the good fight.