WolfishMusings:
You are 100% justified to feel the way you do. People simply don’t know open Halacha in the Shulchan Aruch — especially not only when someone acts like an Am Ha’aretz but when it also disturbs someone else’s davening.
In addition, there is supposed to be NO HEFSEK between the Uva L’Tzion kaddish and the start of Mussaf. So this “neighbor” in shul is wrong on all counts.
Have a Good Chodesh.