Junio C Hamano [off-list ref] writes:

I was wondering about the same thing.  I still see an unwanted "[ ]"
around Kristoffer's e-mail address that will break responding to the
message in your [PATCH v4] e-mail that can be seen at

  https://lore.kernel.org/git/pull.1675.v4.git.1709716446874.gitgitgadget@gmail.com/raw (local)

so, the experiment revealed that it did send some headers were
broken.

This does not necessarily mean GGG is broken.  The majority of the
patches I see here from GGG are without these funny [square-bracket]
around addresses at all, and this was the only patch (or it is
possible that your other patches may have had the same issue; I do
not remember) with that problem.  It might be caused by what you
feed GGG (e.g., the messages you give it in your pull request) that
caused GGG to hiccup, perhaps?