Having guix-patches@gnu.org as the default endpoint of 'git send-email'
seems reasonable when working on the Guix checkout. From my
perspective, it is a useful default to me at least, so without more
information as to how that happened, I'm inclined to close this as notabug
:-).

Here is the information about what happened:

I used --reply-to instead of --to.

This should have happen to tell me about my mistake:

To whom should the emails be sent (if anyone)?

(plus readline prompt)

But nothing happened and the mail went to guix-patches@gnu.org.