The most asinine language arts rule I was ever taught was the spelling mnemonic "I before E except after C." It's weird that such madness could get enshrined as a rule resistant to either educators or bureaucrats. Yet by eighth grade, we've all at least heard it. It reigns supreme despite being the height of counterfeit aids to learning. It's a heinous educational sin.
Alright, how many words in that paragraph? 62 for those who don't want to count. How many violations of the I before E rule? I'm not telling. If you're not sure, drop me a line and I'll tell you. Relatively speaking, there are a lot. Of course the paragraph is silly, but it's grammatically correct and structurally sound, so it works as an example -- besides, it's the best I could do off the top of my head while sitting here at the computer. For the record, the British have expunged the rule from their educational rule book (I think they have a Ministry of Stupid Language Rules).
When I was in elementary school, every week our teacher would give us a list of 10 words we had to learn to spell. The following week, she would give us a test on those words (all of my teachers until junior high were women). By Fifth Grade, the words she chose were invariably those that, in the eyes of an 11 year-old, didn't follow any discernible rule, such as "thought" and "would". I vividly remember having a moment of utter brain lock over the word "caught". I knew she wanted the "I caught a cold" variant, and I knew how to spell it. Somehow, it got diverted along the way when I tried to retrieve it. I finally shrugged and wrote "cot." She'd also toss in some words that complied with I before E, and some that snubbed their noses at the rule.
Her point in all this? The only rule when spelling English is that there are no rules. Spelling English is not easy. I'm not sure that it's even taught anymore, what with the ubiquity of spell check programs and instantaneous online resources like Dictionary.com. If that's true, it's sad. It's like letting teens take their driver's license test without taking a Driver's Ed course because they've played video games since birth. Taught or not, it ought to be a rule that anyone who writes for public consumption must pass a basic spelling competency exam.
Pick a random story here on SOL, and the odds are, you will find at least a handful of misspelled words, but likely as not you'll have to wade through gross lots of them. Personally, I don't care how hard it is to learn how to spell correctly. There is no excuse for more than the occasional typo when it comes to spelling. Turn on your spell check! When a little red line appears under a word, it's misspelled. Right click the word, and the damned program will even give you the correct spelling. Since spell check is hardly infallible (though a damned good starting point), there are back-up resources for those times you're not sure: Online dictionaries, real dictionaries, editors - you know, those fine people who actually paid attention in spelling class, and who now volunteer their services at no cost to the author.
With all these resources, incorrect spelling in a story is inexcusable. And yes, it does matter. Consistently misspelling words shows you don't give a shit about your story. If you don't give a shit, why should I? If you can't be bothered to make an effort with such annoying details as correct spelling, why should I be bothered with making an effort to read your story?
Always remember, it's your responsibility to make sure whatever you're trying to convey to me the reader is clear. It's not my job to decipher your gibberish to figure out what the hell you're trying to say.