There's no contradiction between what I said and what you're saying -- we just happen to want different jobs. I don't want a job which has expectations for clothing beyond "yes please".
It's up to the original poster to decide what sort of job he wants and dress appropriately for that -- odds are, the job he wants is one which neither of us would want.
Incidentally, bad spelling in an otherwise smart person is a good sign of creativity, because it's correlated with personality types that correlate with creative thinking (when intelligence is evidenced at all).
It's the same sort of thing as dyslexia being different at a neurological level in chinese then in english. English dyslexics who learn chinese aren't dyslexic in chinese. Likewise, people who are messy in their english might be extremely good at code. People sure like to hang onto conventional wisdom even when there is plenty of scientific evidence to suggest that they are wrong.
Clumsy use of English from someone for whom it isn't their native language is a completely different matter, I don't care about that.
For me, it's less about the typing or language skills and more about proving that you can produce a complete work-product. A typo-laden resume indicates to me that you failed to have at least one native speaker of the language review it.
If you have a known weak area (English is not your most fluent language and is also required for the job), I would expect a thorough individual to seek help.
Just like I would expect a rock-star hacker to call tech support or post on open-source forums for help if they have a particularly difficult bug that they aren't making headway with.
I agree dress like the job you want to have, but I disagree with the t-shirt bit. I've worked at 4 different companies, and always show up wearing professional, clean clothes to my interview (suit and tie the first time, since then just button down shirts and dress pants or khakis).
The t-shirt and jeans can wait until you've proven yourself for a few months. I go to work now in shorts and a t-shirt, so this isn't some sour grapes rant. Though I dress casual for work, given a choice between two identical, impeccably groomed, candidates one who came professionally dressed and one who came in shorts and a t-shirt (and that being the only difference), I would be likely to hire the one who came like he was here to interview.
Of course, I would hire someone casually dressed who knows their stuff over an idiot who happens to be wearing a suit, but I don't think there's any reason to put yourself at a disadvantage. Don't overdress, don't underdress - wear clothes appropriate for the interview.