I was considering at some point to create a patch to nano to have a simple option to switch to more common bindings or even ask the user on the first run about it. But then I discovered the micro editor and simply have been using that.
I recall the very first time I was thrown into emacs because it was the default at university terminals (around 1993, I think). And I recall the first time I was thrown into nano (I think it was on Gentoo, maybe around 1999).
The difference in UX couldn't have been more stark.
I use vim day to day but I do miss pico's ctrl-k/ctrl-u behavior for doing quick block cut/paste.
When I typed Ctrl-S, I was prompted for a file name. Nano saved the buffer into that file. I then made edits and used Ctrl-S again; it saved again without prompting. Furthermore, if nano is invoked with a filename argument, then Ctrl-S doesn't prompt.
Ctrl-H is indistinguishable from ASCII backspace; if it does anything other than erase the character to the left of the cursor (possibly after climbing to the previous line, if the cursor is at the start of a line), it is objectively, positively wrong.
You can distinguish Ctrl-H from backspace in a GUI system where you get detailed keyboard events. Nano has to work in a terminal.
In the GNU/Linux environment, the standard keybindings are the Emacs-derived ones. Ctrl-A to go to the start of the line, Ctrl-E to jump to the end, ... pasting is called "yank" and mapped to Ctrl-Y.
Your point stands since GNU Nano doesn't stick to these either.
Ctrl-C is interrupt in the TTY environment. This is so entrenched that programs which obtain Ctrl-C as ordinary input rather than a SIGINT signal still use it for interruption. E.g. in Vim, we can use Ctrl-C to interrupt long operations.
Ctrl-V is entrenched as a "verbatim" key: insert the following character literally, even if it is a control character.