Is there an option to email customers a payment confirmation or receipt automatically?
No, there isn't a way to automate that process in Wave currently. Receipts have to be sent manually. Your clients do still have access to their invoices after a payment was recorded, and they'll be able to see the payment there.
I do understand why you would want to automate this process, however. I can't promise a timeline or guarantee that this feature will be added to Wave, but feedback from our users has a significant impact on what we choose to build next. Thank you for taking the time to provide yours.
Please for the love of god make this a thing! When I'm sending out 15-20+ invoices a week and I have customers asking where the payment confirmation is, it becomes a major task.
Edit: Also I love what you guys are doing and do not want to sound demanding by any means!