In the video, the incognito copyeditor (whose face is blurred out) changes “gentlemens outfitters” to the correct ”gentlemen’s outfitters,” and tweaks “motor’s” to ”motors” with a strategically placed sticker.

In English apostrophes are used as shorthand for possession. But there are aspects of their use that are indeed genuinely confusing, as in the common exchange of “it’s”—a contraction of “it is” or “it has”—for “its,” the possessive form.

Then there’s the case of a singular noun that ends in “s.” Some style guides, including the Associated Press, simply add an apostrophe, while others (including Quartz) opt for adding the apostrophe as well as an “s”—”the princess’s return.”

It’s perhaps unsurprising then that ad writers and sign-makers tend to omit or misplace apostrophes. But for grammar sticklers like Bristol’s night vigilante, improperly punctuated signs create a kind of visual itch.

But who cares? Someone who passes by a sign that says “Amys Nail’s” knows that this establishment is run by someone named Amy, and you can get your nails done there.

Perhaps it’s because we spend our childhood drilling on grammar rules, so it pains us to see those rules flouted. “All of grammar and grammar snobbery seem to me rooted somewhat in this very fundamental desire to label things right or wrong,” explained grammar columnist June Casagrande when Quartz interviewed her for an earlier story about the Oxford comma.

Which is perhaps why watching the grammar vigilante is so oddly satisfying. He does what we can’t: reach out and carefully, quietly erase the ugly error.

📬 Sign up for the Daily Brief

Our free, fast, and fun briefing on the global economy, delivered every weekday morning.