kill-buffer is an interactive built-in function in `C source code'.
It is remapped to `ido-kill-buffer', which is bound to C-x k.
I was puzzled [by] what this meant.
Remapping: the "mapping" is between commands and keys. It should be sufficient
to add only a couple of words here to make things clearer. E.g.
Its keys have been remapped to `ido-kill-buffer': `C-x k', `C-M-whatever',...
^^^^^^^^
It is fine for the regular doc, which explains things more precisely and at more
length, to speak of one _command_ being remapped to another _command_. But here
it might be better to speak of one command's key bindings being remapped to
another command.
That said, I don't have a problem with the current help in this context. I
mainly want us to avoid becoming verbose here just in order to make clear what
admittedly could be confusing.