Actually, that is exactly what an editor is for, to find spelling and grammatical errors. No matter where you're writing, you should watch your grammar and spelling.
If you're worried about offending people, you made some extremely rude comments as well, calling the people trying to help your friend ignorant and stupid. Take all comments, both positive and negative, and grow from them, don't insult the people that make them. Raru also never said that there were too many errors, she just commented that one word was spelled wrong, it's a good thing to point out.
I understand that they happen sometimes just because you type it wrong and there's nothing that catches it, but then it shouldn't be a problem to say "oh, woops, my bad" and edit it. I know I've done it before, been informed about it, and promptly laughed about it and fixed it. Getting a spelling error pointed out isn't insulting, it helps you grow as well.
I'm just going to not comment on the backwards writing anymore, I give up on that part.