Talking during chazaras hashatz is a severe aveirah–in the language of the Shulchan Aruch , “the sin is too great to be forgiven ,and he should be scolded “. Note that such a loshon is not found anywhere else in Shulchan Aruch about any aveira.
The Chofetz Chaim writes that many Shuls were destroyed due to this aveira, and therefore people should be appointed to go around the Shul and make sure that this is not happening.(124:7, MB s”k 27)
“When the Ark would journey, Moshe said ‘Arise,HaShem ,and let Your foes be scattered ,and let those who hate You flee from before you’. And when it rested he would say’ Reside tranquilly , HaShem, among the myriad thousands of Israel’ ” (Bamidbar 10:35,36)
These two p’sukim , said when the sefer Torah is removed from the Aron Kodesh and when it is put back, constitute a sefer shalem according to some opinions in the Gemara. This certainly points to its supreme kedusha and intensity.
How sad, then, that people sometimes see this period of time as “down-time” , to talk, to shmuezz, even to joke around! What a corruption of kedusha!