The use of correct spelling and grammar indicates care in the end product. Misspelling and bad grammar do not indicate stupidity, but do usually indicate laziness (except for those for whom the language is not their first language). Spelling pedants may be irritating, but again, what's so hard with proofing a write-up? If you are a student, you proof your work. If you are in any type of business, you proof your work as well. What's so difficult about proofing your work here as well before hitting submit?