On Thu, Oct 31, 2019 at 12:56 PM SZEDER Gábor [off-list ref] wrote:

All the usual warnings about rewriting already published history
apply.  The hash of a couple of commits from 2009 might seem
irrelevant now, a decade later, but after correcting those author and
committer lines the hashes of all subsequent commits will inherently
change as well.  This is, in general, upsetting for everyone who have
cloned the repo and built their own work on top.  Furthermore, some
commit messages refer to older commits by their hash (e.g. in
431dbd98ba: "Simplifies and updates commit
dbef8dd3bf00417e75a12c851b053e49c9e1a79e"); those references will go
stale after rewriting history, unless you put in extra work to update
them.

For completeness for future readers of this thread who have cases when
rewriting history is a valid option, a tool such as Elijah's
git-filter-repo[1] can not only fix the "broken" email addresses, but
also can adjust hash references in commit messages so they don't go
stale.

[1]: https://github.com/newren/git-filter-repo