I have configured a new currency billing site (EUR). In that credits are showing as 10,00EUR instead of 10.00EUR. In other currencies it is showing in point. In mail and invoice also it is showing as a comma only.
Billing site -> https://freshgenie-eur-test.chargebee.com/subscriptions.
When the currency is in Euro, the decimal separator would be a comma and the thousand separator would be a point. This is the general behaviour of all sites with Euro as the currency. Hope this helps!
Thanks for informing us. Our Engineering team is working on a fix for this right now. We will send you an update as soon it's done.