@shambix where are you trying to replace . with ,?
In the input field? If this is the case then the browser is supposed to use the correct character for a decimal point based on the user’s language preference. At lease this is my understanding of the way it’s supposed to work. Unfortunately, not all browsers support this. ACF is simply outputting <input type="number" />
If you mean formatting the number on the front end then I don’t have an answer. ACF does not do any formatting for number fields. Unless you add formatting of some kind ACF returns exactly what is stored in the database.
In both cases, nothing in ACF is setting or altering the way numbers are displayed.
