I'm trying to set up copy/paste actions using ctrl+shift+c/p like it is done in GNOME terminal but for urxvt. I didn't find any simple solution - it seems like it always requires scripts, hacks etc which gets me annoyed when it comes to such a basic things. That's why I'm wondering if it is possible to just change/add some entries in ~/.Xresource to move the default behavior from ctrl+alt+c/p to ctrl+shift+c/p - since the former already works as expected.
Also, there is a lot of notions regarding clipboard itself: X calls them "selections" rather than "clipboards"; there are PRIMARY and CLIPBOARD selections; etc. I don't really understand all these subtleties - so feel free to be verbose!
I use Xorg server with i3 WM if it makes sense and rxvt-unicode v9.22 - released: 2016-01-23
short: no, you can't
longer: I pointed out in Rebinding CTRL-ALT-[C|V] to CTRL-SHIFT-[C|V] in URxvt >= 9.20 that the binding for these is essentially hardcoded in urxvt without an easy way to change them (aside from external scripts or modifying the program itself).