Hmm. I'm not sure about this. From my experience people are a lot more likely to speak their mind or engage in highly emotional behavior online, but in-person are a lot more reserved than you would think based on what they say online.
I'd believe that habit of thought could transfer to offline life, e.g. worrying about getting caught at a strip club, as per the paper.
In a level 3, you'll say anything. You don't care, you may or may not believe it, but you'll say it.
In a level 2, like social media, you'll say things you wouldn't say in real life, but you'll still moderate some of what you say because your peers will see it and maybe they'll disapprove publically.
Level 1 would be your in person communication. This is going to be highly moderated compared to l2 or l3. You certainly won't say things in person that you would say online.
To me this seems makes sense.
Social media are useless for any serious discussion unless you have pseudonymity (HN, reddit) or full anonymity (4chan).
Sure, the site administrator, your ISP, or the NSA may know it's you posting, but the other users of the site don't. And you don't have a site wide identity that follows you around. Unless you explicitly choose so.
For me, it's got nothing to do with anonymity or some possible later repercussion; rather, it's being sensitive to short-term feedback. Effectively, the bandwidth of human communications through the internet is low and error-prone, and hence stressful for me to get my thoughts across. (It doesn't help that long-form replies -- which help me explain my ideas better -- have been grossly devalued.)
Sadly, it's gotten worse in the last few years -- perhaps due to Facebook, or perhaps due to societal changes that opened the door to mediums like Facebook.
I seem less and less capable of growing that thick skin that people always talk about...
Every tweet is like an underdetermined system of equations with infinitely many solutions (solution == what they really meant when they typed up the tweet, and everything else that readers project onto posters). Everyone has to choose how to interpret ambiguous statements all the time, and by nature our brains are more likely to choose interpretations that conform to our own expectations.
We can create our own private echo chambers if we aren't careful, where we always interpret what people who are on "our side" say in the most charitable way possible, and we always interpret statements from opponents in terms of the biggest strawmen our brains can come up with. This is a pitfall of any sort of communication, but it seems to be a vastly greater danger with online communication.
People tend to blame the lousiness of online communication on other people, and there's some truth to that, but I think it's just inherent in both the medium and human nature. In the long term I hope that digital mediums can evolve to support better communication and provide more fertile ground for more constructive discussions.
When you put it out in public online, it might persist unaltered for years or even decades. My most upvoted comments under an old pseudonym on YouTube caused me to decide to never, ever look up old posts on Usenet.
Online is an entirely different story. The barriers to communicating efficiently makes people default to pattern-matching instead of thought, which pretty quickly devolves into the lowest common denominator of conversation.
As you say, places like reddit are better for this, where people have a higher tolerance for longer conversation and the interface supports longer posts. I'm part of a subreddit that's probably in my top 3 fora ever for quality of conversation ever, but it relies heavily on the fact that the norms are pretty well-internalized by everyone.
Almost as though people exhibit adherence to a culture just to perpetuate that culture itself rather than their own identity (of which there is none).