Specifically, I am curious if, in the words of a commenter on r/law, there is any substance to the idea that there was a reluctance to sort by ideology caused directly by the scars of internecine violence in the civil war
While you wait for an answer to your specific question, there is an entire section of the AskHistorians FAQ dedicated to how the different coalitions coalesced into the modern Democratic and Republican parties over the course of the later 19th and 20th centuries.