>? The source of what?

I mean the emacs package in guix source, the emacs-next package, precisely.

>> will record its modification of EMACSLOADPATH in profile,
>
>Where is it recorded?  Which modification?  What is "EMACSLOADPATH in profile"?

The package definition of emacs-next has native-search-path field, which add customized EMACSLOADPATH environment variable.
And I guess it modified ~/.guix-profile/etc/profile.

If you still doesn't understand, please ask me again, thanks!