I am facing an issue where the DAX FORMAT formula is not honoring the locale of the user. For example, in Dutch, the thousand separator is typically a dot (.) while the decimal separator is a comma (,).
If you add show a numerical measure on a card and you enable the thousand separator it correctly honors your locale. As you can see in the screenshot, the thousand separator is a dot (.). So far so good!
If you then create a more complex measure where you use the DAX FORMAT formula to convert a number to a string indicating that the string should contain thousand separators, Power BI does not use the correct thousand separator. So you have a discrepancy in behavior.
Thousand separator. In some locales, a period is used as a thousand separator. The thousand separator separates thousands from hundreds within a number that has four or more places to the left of the decimal separator. ... The actual character used as the thousand separator in the formatted output depends on the Number Format recognized by your system.
The first thread indicates that the FORMAT function follows the locale format of the model (aka the model language).
I can confirm that this is indeed true. If you change the model language of your PBI desktop installation, and you start a BRAND NEW report, the separators used by FORMAT follow this language. However, this does not make sense at all. I understand that there should be an internal format (which should not be changed), but the format displaying towards the user should follow the format of the user, just like the normal measures already do.
So to summarize:
* Discrepancy between displaying of normal measures vs. measures using the FORMAT formula. ---> BUG
* Documentation about FORMAT formula is incorrect --> WRONG DOCUMENTATION
Please let me know if I can help solving this issue.