Now anyone can edit client message in the ticket - so a customer can send us a mail - and we can change it without a problem to something different .
Please add a permission per Administrator Role - to restrict deleting and editing of customer email in the ticket system. there should be one permission to edit emails and another permission to delete it. this permission should not be connected to the Delete Ticket permission.
As for Private Note - Please add a permission per Administrator Role to allow someone to edit his Private Notes (only his Private Notes - not all of them) and another permission to delete a Private Note (again - only his Private Notes) and another permission to do it for all the Private Notes regardless of the note writer.
to sum it all up:
I think that there should be separate permission to delete or edit customers replies - such an option is highly sensitive permission - since changing customers replies without any trace or way to see the original message from the customer can lead to some trust issue and maybe law suit from customers.
Another and separate permission should be related to adding / deleting / editing customers notes (in the customer profile)
and yet another and separate permission should be related to adding / deleting / editing notes in the ticket system.
such a permission should be set as: no permission to delete a ticket note at all, can delete his own notes only, can delete any note.