Found the solution.
Hello again! :)
I've found the solution.
I just had to:
1. Click the "Settings" tab in the admin panel.
2. Then click the "Preferences" tab.
3. Go down to "Email settings"
4. Remove the mark from "Strip Quoted Reply".
5. Remove the text "-- do not edit --" from "Reply Separator Tag".
And it now dosn't show the "-- do not edit --" text in the "Ticket Reponse/Reply" emails sent out.
Thanks for helping! :)
Warm greetings
Klaus Hundal