By far the worst was a woman who worked at the Software Engineering Institute. She was a brand-new hire from CMU, one of the top-rated computer science schools in the country, or perhaps the world. She had written
printf("The value is %d," value);
and the compiler was giving her a syntax error. I spotted it (can you? Go take a look...) in seconds.
So I said to her, "you transposed the comma and quote mark" and walked away. A few minutes later as I passed back she told me it still wouldn't compile. So I saw the same error, and said "You have to put the comma outside the quote mark". She looked at me, and in perfect sincerity said "But the comma always goes inside the quote mark!". I started to explain to her that no, it was a parameter separator and had to go outside the quote mark, and she interrupted me to insist the code was syntactically correct. Everyone knows the comma belongs inside the quote mark! Why, her English teachers had downgraded her text when she put the comma outside the quote mark!