V, bottom line you need to recognize is that the spelling and typing problems lost a lot of readers right away. I read the original post three times, and could not tell you more than the vaguest notion of what you were saying because the spelling and typing errors that went uncorrected drowned out the actual content and convinced me you didn't really care about that content if you weren't willing to go to the trouble of such a basic operation as spell-checking.
If you want your reader's time and effort, have enough respect for your audience to do such basic things to eliminate that distraction. Otherwise, you're conveying the message that you're just SO special you don't have to be bothered with clear communication and your reader owes it to your wonderful intentions to struggle through mistake after mistake. Hard to see those good intentions when the mistakes are shouting "I couldn't be bothered".
Another point (which my mother makes in connection with poorly written restaurant menus), if you're not willing to make the effort to get the spelling right, what other details are being skipped, skimmed over, or ignored? In the case of a poorly written letter to the editor, the mistakes give the reader the impression the writer is paying so little attention that factual accuracy is probably suffering too. With restaurants, as my mother puts it, "if they can't get the menu right, what are they doing to the food?"