In order not to duplicate comments it at least seems to be possible to for agents to to edit the comment and changing it from internal to external.

The issue is, that this seems not to trigger notification to the customer as it does when a new comment to the customer is written.
How to configure this? Is it even possible? Or does it need to be automatized? And if it needs automation, how can it be send in a way that the customer can reply to the email the same way as he can for the standard notification mails (it seems to come from a different sender)