Hello Markus,
In the Microsoft documentation you linked, the name "text qualifier" is misleading. It doesn't mean the value will always be formatted as text by the program. For example, I tried making this CSV:
ID|T1|T2
"01"|"April 6, 2022"|"01234567890123456789"
In a new spreadsheet in Excel, I imported the CSV with the custom delimiter pipe (|), and all three of the values were interpreted as formats other than text. "01" became the integer 1, "April 6, 2022" the date 4/6/2022, and the long number became 1.234567E+18. So adding double quotes around all values to designate a "text" datatype will not work for Excel; users still need to manually change the formats of the cells.
Also, a user might want "April 6, 2022" to be interpreted as a date for calculations, so whitespace in a value doesn't necessarily mean it's supposed to be treated as text.
The current behavior of BaseX will output a CSV that can be correctly interpreted by both Calc and Excel with the correct separators/delimiters set, so I don't believe it should be changed, and even if it were it wouldn't accomplish what you want.
-Tamara