IIRC, in_quote only matters here in CSV mode (because CSV fields can have embedded newlines). So why not just forbid parallel copy in CSV mode, at least for now? I guess it depends on the actual use case. If we expect to be parallel loading humungous CSVs then that won't fly.
Loading large CSV files is pretty common here. I hope this can be supported.
Thank you for your inputs. It is important and valuable.
