You mean in the filter header row? Characters entered in the input box aren’t directly replaced, but the user’s input is automatically parsed into numbers according to the column’s format and localeFmt settings.
For example:
"." is used as the decimal separator in en-US
"," is used as the decimal separator in de-DE
So, as long as the localeFmt and format are correctly configured, numeric input with the appropriate decimal symbol will be parsed correctly.
If your users belong to different locales, you can leave localeFmt empty — the decimal symbol will then automatically adapt to each user’s system locale.