He's clearly not fully illiterate since he's been able to post on this forum and, you know, use computers in general, but on the other hand some of his posts are borderline unintelligible (he once misspelled "Deagle Nation" as "Deagle Nagion"...) and he's not online very often; he posts to Twitter only very rarely, and his Steam isn't even that active at all, only going on once every few weeks to play a game for an hour or something before logging off again. Given this, my theory is he enlists other people's help when extensive reading/writing is required and otherwise he just doesn't bother trying; either that or he can read a sentence, it just takes him a while to do so and great effort. But then again, these are just shots in the dark. We really don't know specifics about his entire reading situation beyond the fact that it's impaired.