At most (maybe even all?) Conservative synagogues, the congregation remains seated during every kaddish (except mourner's kaddish, and then only mourners rise). At Ashkenazic Orthodox synagogues, the entire congregation rises for every kaddish. The question: Does anybody know how far back this difference goes, and why it originated? Back in the 1940s, for example, was the difference in practices already in place? What about in the early 1900s? Can the difference in practice be traced to older halachic traditions (e.g. "The Shulchan Aruch says X but the Rema says Y"), or is there some subtle ideological point being made?
This question of sitting vs. standing for kaddish was raised in Is it required to stand during Kaddish? but there the context seems to be only Kaddish Yatom, and I am interested in the other instances of kaddish as well; also, my question is not so much about the halacha as it is about the historical point of divergence in practice between Orthodox and Conservative congregations in the United States.