poor comma usage

Very soon, I'm going to do a post about how to use commas, but for the moment, let's look at the following sentence, which I found over at Instapundit:

The standing ovation Ansari gets at the beginning of his show, and the hearty reaction to his anti-woke new material, are heartening.

The verb "are" in the predicate "are heartening" is ungrammatical. I can see why the writer wanted to use "are," though: the writer was thinking his sentence contained a compound subject. Compound subjects, taken as a whole, are grammatically plural. Some examples:

• Bill and Ted have an adventure inside an elephant's colon. (not has)
• Fuchsia and Mauve are what I named my testicles. (not is)
• Karate and eating pussy are essential skills for survival in the woods. (not is)

Basically, with a compound subject, two subjects joined with the coordinating conjunction "and" together form a plural subject, and this must be reflected in the verb.

But what happens when you take the second part of a compound subject and wall it off with commas? What you've created, at that point, is a parenthetical expression (which can also be walled off by em dashes [ — ]). A parenthetical expression is NOT part of a compound subject, so the verb needs to reflect the singular:

• "Silence—and obedience, too—is golden," said the child molester. (not are)
• His fart, and the horrified silence that followed it, was pleasing to Gerald. (not were)

See how that works? It's tempting to treat a subject + parenthetical like a compound subject, but it isn't one. To remedy that, either remove the commas or change the form of your verb. You might risk creating a run-on if you take out the commas, but that's preferable to being outright ungrammatical.* So: two solutions to the first sentence quoted above:

1. The standing ovation Ansari gets at the beginning of his show and the hearty reaction to his anti-woke new material are heartening. [remove commas]

2. The standing ovation Ansari gets at the beginning of his show, and the hearty reaction to his anti-woke new material, is heartening. [change "are" to "is"]

One "exception" that's not really an exception is when your compound subject involves a list of three or more nouns and/or noun phrases. In that case, commas are permissible.

• Sleepy, Bashful, and Grumpy have all had their way with Snow White.
• Sloth, Greed, and Lust are what she named her three boobs.
• Six cats with leprosy, two one-eyed horses, and a syphilitic gecko all walk into a bar.

[That last sentence shows common nouns embedded in noun phrases.]

Hope this helps.

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*I don't think run-on sentences are perforce ungrammatical. Mostly, they're just overlong.