I’ve seen this in almost every shul:
1) By hoitzo’as sefer Torah, one or more people repeat “Gadlu la’H-shem iti” after the chazan
2) When the sefer Torah is returned, some people repeat “Yehalilu es shem H-shem” after the chazan.
The above occurs so often, I wonder if there was some old minhag to daven this way.