When doing email-based development, it's not uncommon to put things after a --- line which you want to be in the patchbombed email, but not in the final commit. For instance:

Frob the googleblarf
<description>
Signed-off-by: Joe Smith <joe@smith.com>
---
I thought about blarfing the googlefrob as well; let me know if that's desired.
CC: Amanda Hug <hugz@gmail.com>
CC: Tom Thumb <tiny@carrot.net>

In this case there's a comment to reviewers, as well as people to automatically CC when sending the mail, none of which you want to be committed; because git am will automatically strip it.

It used to be that you could add this when doing a stg refresh, and it would remain; but now anything like that seems to be deleted on refresh -- making stackgit much less useful for email-based workflows.

$ stg version
Stacked Git 2.0.4
Copyright (C) 2005-2022 StGit authors
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
SPDX-License-Identifier: GPL-2.0-only
git version 2.38.1