The Darkei Moishe (O.Ch.125) writes that the Maharil
didn’t talk from the beginning of Kedusha till after
the Amein of Hokeil Hakodosh.
It seems that during Chazaras Hashatz he would
talk, as long as it was past Hokeil Hakodosh.
The Kaf Hachayim explains that this would have
been only when he wasn’t Davening with that
Minyan*, otherwise you may not talk during the
entire Chazaras Hashatz.
* דבר פשוט only where he is not disturbing other Mispalleim. אמבצי