I suppose I've got just a normal third world education, but even with my poor background I considered the cats example somewhat extreme. Is this kind of thing really common?
And yes, at least in my area (Southeast USA) people do not know punctuation rules. Most of them write okay, but comma splices, apostrophes, semicolons, etc. would trip them up.
That's because it is unbelievable. In high school in the US, I had to write an essay per week in my history classes and a paper per book in my literature classes.
I went middle ranked suburban high school (and a large public university). Based on my experience, this story didn't happen the way it's being told.
I think it's more likely that no one wanted to raise their hand because they thought it was a trick question.
I've always enjoyed learning and I think anyone who does can succeed in any environment. There were certainly other kids who strived for more even in the country and did okay too. But having moved a lot I could tell the difference.
I also was told that non-native speakers can better distinguish between 'well' and 'good', and the usual suspects 'you', 'your', 'you're'. The latter is so basic that I am bewildered when native speakers cannot understand the difference.
In the UK it is, the cats example would stump a lot of people.
A classic here is 'its' and 'it's'.
Not surprising, even looking at some of the appalling written English posted here on HN (a community which, you would think, is educated to an above-average level). Nobody cares. Plus, if you actually point out incorrect spelling, grammar, or usage here, you’re instantly shouted down with cries of “language evolves!”
[Edit: Looks like the “Language Evolves” crowd is already here!]
If you really care about improving some one grammar, send a private message. It can be very useful for a non-native speaker, especially if it's not a total stranger to you. Saying out loud "fix your grammar" doesn't make you a hero on a white house.