I would read that study as coding standards lead to profanity. (Not sure wether or not coding standards should be correlated with code quality, I just think it is obvious that the measure is correlated with the conclusion in an obvious way.)
[Post posting:] Also looking at the plots, it seems that the two distributions are different, first the swear word distribution seems to be wider and second it has a clear outlier at "software quality" 8, so if anything it is an indication that something much more complex is going on.