Spelling and punctuation: Some writers, especially neophytes, think that these things are just 'mechanical details', boring and unimportant.

Those people are wrong.

in point of fakt spellling and punkshuation can make a bigg diffrins in how a reeder reacts to your story mechanikle details they may be but if you skroo up thoz details the rederz gunna think yer not much uv a rytter and yu no wut the rieder will be rite to think so

Get the point?

Now, if you blow off the standard rules of English (or whatever language you write in), it's one thing if you do so deliberately and intentionally. However, it's something else again if you just couldn't be bothered to proofread your manuscript. Substandard English, whether it be deliberate (see also: Flowers for Algernon, by Daniel Keyes , or The Adventures of Huckleberry Finn, by Mark Twain) or otherwise, will influence how the reader thinks about your characters and your story; the difference is whether or not you wanted to subject your readers to that particular influence.

At this point, I can hear someone in the back row complaining about how this 'punctuation and spelling' stuff is arbitrary and senseless, and why should he have to shackle himself to the bounds of mundane convention?

Well, do you want other people to (a) read your stuff, and (b) understand what they've read? If you can honestly answer "No" to both of those questions... you're right. Because any 'no -- no' person is clearly writing solely and entirely for himself, and if you fit that profile, you shouldn't be concerned with anybody else's effete, bourgeois notions of what does or does not constitute 'proper' language use. But if you answered 'yes' to either one of those questions? That is why you should worry about 'proper' language use.

Written communication is difficult enough when everybody concerned agrees on the ground rules. When a writer violates those rules, he's putting obstacles in between himself and his audience; when he does so by accident or through simple laziness, it's needless obstacles he's erecting.

Bottom line: Don't go out of your way to make life hard for yourself. Proofread your stories, or have someone you trust proofread them for you, before you release them on an unsuspecting world.