i have a scientific observation that involves myself observing things
everyone I have ever heard complain/nitpick/freak out about - grammer, spelling, punctuation, etc. are slow readers with poor or average reading comprehension
everyone that I know that spells/punctuates/grammers badly, or doesn't care about that stuff- are fast readers with very good reading comprehension
I admit I don't know tons and tons of people, but of the people I know, this is true