Here are two versions of the same sentence:

The summer of 2022 when this evaluation is happening is before the model launched.

The summer of 2022, when this evaluation is happening, is before the model launched.

Same words. The second one works. The first one wobbles. The difference is two commas — and what they’re doing isn’t decorative. It’s structural.

Here’s the test that makes this concrete. Pull the middle phrase out entirely:

The summer of 2022 is before the model launched.

Still true. Still clear. The phrase “when this evaluation is happening” is a passenger, not a driver. The sentence stands without it.

That’s exactly what commas signal. They tell the reader: this phrase is supplemental. The anchor is on either side of it. Don’t confuse the cargo for the engine.

You can feel it another way — swap the commas for dashes or parentheses:

The summer of 2022 — when this evaluation is happening — is before the model launched.

Works perfectly. Which confirms what the commas were doing all along: marking a parenthetical, not a definition.

Without the commas, the clause masquerades as essential. The reader’s brain tries to use it to identify which summer of 2022 — as if there were several. There aren’t. But missing commas issue that instruction anyway. The sentence becomes a map with a wrong road on it.

This is how flattened hierarchy accumulates in prose. No single instance breaks anything. But a piece full of passengers promoted to drivers is exhausting — everything seems equally weighted, and the reader has to reconstruct the structure you should have given them.

Two commas is a small fix. What it represents isn’t small: a writer deciding what’s central, what’s supplemental, and marking the difference explicitly.

That’s not punctuation trivia. That’s the difference between a writer who thinks about structure and one who doesn’t.