From: Rabbi Akiva Eiger
To: Unknown recipient
Rabbi Akiva Eiger defends the Maharach"sh's ruling that a city-name change in a get is only a rabbinic invalidation, not a Torah-level one, by demonstrating from Tosfos that even personal name changes in the Mishnah are merely d'Rabbanan. He further argues that even the lenient Ba'al HaIttur position on father's-name changes is no longer operative today, since contemporary court practice has made witness signatures implicitly attest to all such details.
Source: Shu"t Rabbi Akiva Eiger §120