git-am -s will avoid duplicating the last signature in a patch. But given a developer creates a patch, send it around for acks/other signoffs, collects signatures and then does a git am -s on a different branch, this sort of sign-off chain is possible: Signed-off-by: Original Developer <od@xxxxxxxxxx> Acked-by: Random Developer <rd@xxxxxxxxxx> Signed-off-by: Original Developer <od@xxxxxxxxxx> Should there be an option to avoid duplicate signatures in a sequence where an author can git-am the same patch? sequencer.c:append_signoff() has a flag for APPEND_SIGNOFF_DEDUP sequencer.c:void append_signoff(struct strbuf *msgbuf, int ignore_footer, unsigned flag) but builtin/commit.c: append_signoff(&sb, ignore_non_trailer(&sb), 0); doesn't have an optional use mechanism available.