Different countries use different symbols as a decimal or thousands separator.
Some use a period, others a comma. Take a look:
Depending on how Survey123 field app interprets these symbols, this can lead to data loss.
Supposing the expected decimal separator is a comma, Survey123 behaviour is the following:
|Value typed in a survey||Value actually stored in the Geodatabase|
As you can see, if the user thinks the correct decimal separator is a period or simply forgets what is the correct one, we'll end up having wrong values in the geodatabase. This is problematic.
Survey123 web interface already has the solution: it doesn't allow you to type the thousands separator.
So... bring it to the app too!