emacs -Q foo.cpp&
type, for example, #include, select it with the mouse then issue
comment-region with C-c C-c, the selection is instantly commented out
Yes. `comment-region' sees the region that you selected, as it
should, and when you invoke it, comments that region out.
(emacs)CUA Bindings says
The command `M-x cua-mode' sets up key bindings that are
compatible with the Common User Access (CUA) system used in many
other applications. `C-x' means cut (kill), `C-c' copy, `C-v'
paste (yank), and `C-z' undo. Standard Emacs commands like `C-x
C-c' still work, because `C-x' and `C-c' only take effect when the
mark is active (and the region is highlighted). ...
Following your instructions, the mark is active, so C-c should mean `copy'.
Info goes on to say
To enter an Emacs command like `C-x C-f' while the mark is active,
use one of the following methods: either hold `Shift' together
with the prefix key, e.g. `S-C-x C-f', or quickly type the prefix
key twice, e.g. `C-x C-x C-f'.
Both `S-C-c C-c' and `C-c C-c C-c' succeed in commenting the region.
Hello! Don't know if this is a bug or if this is supposed to
happen ...