slayven is a dumb
Nah, ability to spell or articulate yourself isn't indicative of intelligence. 
It's true that most smart people aren't grammar and spelling nerds. Everyone misspells sometimes, and a lot of very smart people misspell a lot.
But I think once you fall below the threshold of writing competence, you find a strong correlation with people who have a hard time learning. It's not dispositive, but the general correlation is there.
That said, Slayven to me mostly just verbally has a stutter and doesn't enunciate very well, and in writings he misspells things a lot. I wouldn't say he falls below that threshold of competence. Well, maybe he's on the edge of it.