Summary

When using CSV Export and the issues have a number field that contains a decimal value, the CSV file will show the value always with the English decimal character which is (.) even if the language in Jira system settings and in the user's personal settings is not English.

Example:
In Jira:

• Number field= 5,2
  In the CSV file:
• Number field= 5.2

Workaround

You can use the "Export to HTML Report (current fields)" option. Change the extension to XML. Then in Excel, you can use "From XML Data Import" to import the data. There will be some header and footer rows, but the numbers containing commas will be imported correctly.