Lets see. The first link of yours shows that the study is limited to Irish 15 year-olds and was conducted 4 years ago. The second link describes "children in disadvantaged schools" which would make sense if you compare them to children in middle-class or high-class schools. Actually that would make the tolerance towards not-well-written posts higher, than if one from the high-class school wrote a bad post.

Personally I'd take any official "loose" studies like these, with a grain of salt. I remember an official study a few years ago, saying that bananas cause cancer. That must mean its fact, right? Shit I better stop eating those long yellow things..oh wait..I have for almost 30 years and I havent got cancer.