Whatever it is, it's not CSV

The plug-in has given me a hard time but I finally managed to import the categories.

The main reason I had troubles was the file format used. A proper CSV file uses a single character to separate fields and – if necessary – uses double quotes around strings containing the separator character. But the real problem turned out to be that the file format is mixed up with ideas from HTML: to use an ampersand in you category name, you have to use the HTML entity &. That’s not documented and certainly has nothing to do with CSV. And it isn’t necessary either.

When the import had gone wrong, I used the same file to delete the categories that hadn’t been properly imported. But I didn’t work. The plug-in obviously interpreted the same file differently for the deletion and deleted hardly any categories.

Next I tried to do some reverse-engineering: I created a small tree of categories and tried to export them to see the undocumented file format in use. However, it exported just the top category. All other categories were missing from the file. That changed once I used the categories to tag posts.

But after a few wasted hours, I had my categories imported as desired.