"Tony Tung via GitGitGadget" [off-list ref] writes:

quoted

From: Tony Tung <redacted>

Instead of using the hardcoded `# `, use the
user-defined comment_line_char.  Adds a test
to prevent regressions.

Good spotting.

Two observations.

 (1) There are a few more places that need similar treatment in the
     same file; you may want to fix them all while at it.

 (2) The second argument to strbuf_commented_addf() is always the
     comment_line_char global variable, not just inside this file
     but all callers across the codebase.  We probably should drop
     it and have the strbuf_commented_addf() helper itself refer to
     the global.  That way, if we ever want to change the global
     variable reference to something else (e.g. function call), we
     only have to touch a single place.

The latter is meant as #leftoverbits and will be a lot wider
clean-up that we may want to do long after this patch hits out
codebase.  The "other places" I spotted for the former are the
following, but needs to be taken with a huge grain of salt, as it
has not even been compile tested.

Thanks.

 sequencer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git c/sequencer.c w/sequencer.c
index d584cac8ed..33208b1660 100644
--- c/sequencer.c
+++ w/sequencer.c

@@ -1893,8 +1893,8 @@ static void update_squash_message_for_fixup(struct strbuf *msg)
        size_t orig_msg_len;
        int i = 1;

-       strbuf_addf(&buf1, "# %s\n", _(first_commit_msg_str));
-       strbuf_addf(&buf2, "# %s\n", _(skip_first_commit_msg_str));
+       strbuf_addf(&buf1, comment_line_char, "%s\n", _(first_commit_msg_str));
+       strbuf_addf(&buf2, comment_line_char, "%s\n", _(skip_first_commit_msg_str));
        s = start = orig_msg = strbuf_detach(msg, &orig_msg_len);
        while (s) {
                const char *next;

@@ -2269,8 +2269,8 @@ static int do_pick_commit(struct repository *r,
                next = parent;
                next_label = msg.parent_label;
                if (opts->commit_use_reference) {
-                       strbuf_addstr(&msgbuf,
-                               "# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
+                       strbuf_commented_addf(&msgbuf, comment_line_char, "%s",
+                               "*** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
                } else if (skip_prefix(msg.subject, "Revert \"", &orig_subject) &&
                           /*
                            * We don't touch pre-existing repeated reverts, because