RE: [External] : About the key binding convention: C-x is reserved by emacs itself whereas the C-c prefix is used for user defined keybindings.

[Drew Adams <drew.adams@oracle.com>]

> There is the convention that the C-x is reserved by emacs itself
> whereas the C-c prefix is used for user defined keybindings.

No, there is NO such convention regarding C-x.
No key bindings are "reserved by emacs [for] itself".

The only "reserved" bindings are those reserved for
users.  (And users can bind any keys they want;
they're not _limited_ to the keys reserved for them.)

This post of mine states the situation clearly (IMO):

https://emacs.stackexchange.com/a/42166/105

(It's the accepted answer to the question you cited.)

Wrt C-x, it says this:

  You'll note that there is no convention regarding
  C-x.  An unstated convention, or just good
  advice/practice is this one, however: If you
  replace some existing, standard Emacs binding
  (i.e., one that you get from Emacs as distributed,
  without loading any 3rd-party libraries) then that
  might confuse or annoy some users of your code.