Prevent mail (commerce_order_receipt) on manual order placement

Yeah, this is a weird one. I don't know why order placement was selected instead of checkout completion. That would seem the more natural event to subscribe to for sending a receipt.

@rszrama: Always the same reason I guess... Checkout completion event was introduced after the event subscriber for sending the receipt was written.
Also, if for whatever reason the checkout completion event isn't properly fired, the receipt wouldn't be sent I suppose?
I'm wondering if skipping the redirect to the site after an offsite payment can cause the checkout completion event to be fired?

If we change this now, then I guess an extra step would be needed in the UI to send the receipt, so definitely a "breaking" change.

FWIW at the time we considered it an absolute requirement that manually placed orders can also get order receipt emails, as not supporting that was considered notable in 1.x.

I think there will always be users in both groups (who want and don't want the email to be sent).

I agree completely with comment #4, if we change this now, then we'll get issues opened about the receipt not being sent for admin orders.
Ideally, we'd have a checkbox from the state transition confirm form modal that toggles whether the receipt gets sent.