How to punctuate sentences like "I'm just calling a spade, a spade."

I was browsing Area 51 and I saw this comment:

I'm just calling a spade, a spade.

I'm never quite sure how to punctuate sentences like these where a phrase is repeated back to back, without any other words to separate them. Not putting punctuation feels weird, but so does adding a comma. Neither intuitively read like I would say them in a conversation.

With a comma, I would pause before reading the second "a spade"; without punctuation, the inflexion in my voice would be off.

So, is "I'm just calling a spade, a spade." properly punctuated?

You don't need the interposing comma. Just say

I'm just calling a spade a spade.

The Subaru commercials get this awkwardly wrong:

It's what makes a Subaru, a Subaru.

No comma needed there either.

Compare the idea using two other nouns.

I'm calling a spade a shovel.

You would never use a comma there. And just because the nouns are the same doesn't change the sentence structurally.

You don't use a comma. I agree it looks weird, but there is no pause or separation of ideas.

"I'm just calling a spade a spade" is the correct punctuation.