The study (PDF) identifies “general trends in the (in)civility and complexity of political discussions occurring on Reddit between January 2007 and May 2017 — a period spanning both terms of Barack Obama’s presidency and the first 100 days of Donald Trump’s presidency.”
The study was conducted by Rishab Nithyanand of the Data & Society Research Institute along with Brian Schaffner and Phillipa Gill of the University of Massachusetts at Amherst. The study examined Reddit, which is the fourth most visited website in the United States with more than 230 million people using the site each month.
We can see the lack of civility and low writing level here on the forums also, mainly from right-wingers. From the article:
Since the end of the primaries (June 2016 – May 2017), complexity of discourse in Democratic subreddits improved to a 6.9 grade-level while discourse in Republican subreddits further declined to a 1.1 grade-level.
This is evident on these forums also, not just on Reddit. I see the cause as right-wingers "argue" without facts, logic, or nuance. There's really no way to have discourse, especially intelligent discourse, when one side denies facts and redefines words to their own odd meanings.