The locale `de_DE` erroneously uses '.' as its thousands (group) separator, which was only used historically. As per DIN 1333, DIN 5008, and EN ISO 80000, the separator is a thin space. DIN 1333 explicitly forbids the usage of '.' to group thousands, and EN ISO 80000 explicitly excludes all other characters than a thin space. For further information, please also refer to the relevant section on Wikipedia at [1] (German). [1] https://de.wikipedia.org/wiki/Zifferngruppierung#Zur_Problematik_von_Punkt_und_Komma_f%C3%BCr_Tausender-_und_Dezimaltrennzeichen
The locale information is in Qt, which in turn uses CLDR data. I suggest to report this issue directly to Qt developers via https://bugreports.qt.io/