Reusing a mailing can result in the wrong "reply to" address

If you reuse an existing mailing, but change the "From" address, the "Reply-to" address isn't also updated. Since the "Reply-to" address is by default a hidden field that's set equal to the "From" address, this leads to the unexpected situation where the "Reply-to" address will differ, and the problem will be invisible to the user.

My client worked around this by enabling the "Allow custom Reply-To" option in the CiviMail "Mailer Settings", but I wanted to report it for the sake of documenting it.