This is basically the same question as here: How to set ctrl+c to copy, ctrl+v to paste and ctrl+shift+c to kill process in xfce4-terminal?, but not a duplicate, because neither of the answers helped.  Alex Kaszynski's answer suggests modifying the ~/.config/xfce4/terminal/accels.scm file.

I did that: I have changed two lines:

; (gtk_accel_path "<Actions>/terminal-window/paste" "<Primary><Shift>v")
-->
; (gtk_accel_path "<Actions>/terminal-window/paste" "<Primary>v")

and

; (gtk_accel_path "<Actions>/terminal-window/copy" "<Primary><Shift>c")
-->
; (gtk_accel_path "<Actions>/terminal-window/copy" "<Primary>c")

but neither of those helped; the interrupt is still assigned to Ctrl+C.  (I would probably need to make it unbind and rebind to Ctrl+Shift+C, but do not know how to do so.)

1. How to map "copy" from Ctrl+Shift+C to Ctrl+C
2. Remap interrupt from Ctrl+C to Ctrl+Shift+C
3. Remap "paste" from Ctrl+Shift+V to Ctrl+V