Wouldn't one normally associate a default with

some sensible setting worth looking into most times?

Perhaps this could be a user setting.

I see. So the use case is to be able to check what

the default value is, so you can try to understand

why it's considered particularly useful.

For that, I'd think that `M-n' suffices, to see

what the default value is (the first default value,

if there are several).

Again, the default value need not even be one of

the choices (completion candidates), in the case of

lax completion (e.g. `C-x b'). I'd think that the

best way to find out what the default is would be

`M-n'.

(Just one opinion, and I may still be missing something.)