https://unicode.org/reports/tr35/tr35-numbers.html#Number_Format_Patterns:~:text=The%20grouping%20separator%20may%20also%20occur%20in%20the%20fractional%20part%2C%20such%20as%20in%20%E2%80%9C%23%2C%23%230.%23%23%23%2C%23%E2%80%9D.%20This%20is%20most%20commonly%20done%20where%20the%20grouping%20separator%20character%20is%20a%20thin%2C%20non%2Dbreaking%20space%20(U%2B202F)%2C%20such%20as%20%E2%80%9C1.618%E2%80%AF033%E2%80%AF988%E2%80%AF75%E2%80%9D.%20See%20physics.nist.gov/cuu/Units/checklist.html.
https://unicode.org/reports/tr35/tr35-numbers.html#Number_Format_Patterns:~:text=The%20grouping%20separator%20may%20also%20occur%20in%20the%20fractional%20part%2C%20such%20as%20in%20%E2%80%9C%23%2C%23%230.%23%23%23%2C%23%E2%80%9D.%20This%20is%20most%20commonly%20done%20where%20the%20grouping%20separator%20character%20is%20a%20thin%2C%20non%2Dbreaking%20space%20(U%2B202F)%2C%20such%20as%20%E2%80%9C1.618%E2%80%AF033%E2%80%AF988%E2%80%AF75%E2%80%9D.%20See%20physics.nist.gov/cuu/Units/checklist.html.