Sometimes people interpret the term too generically and actually implement a high degree of non-trivial, very idiosyncratic complexity, while still calling it "CSV".

One project I worked on involved a vendor promising to send us data dumps in "CSV format". When we finally received their "CSV" we had to figure out how to deal with (a) global fields being defined in special rows above the header row, and (b) a two-level hierarchy of semicolon-delimited values nested within comma-delimited columns. We had to write a custom parser to complete the import.