I think spelling and grammar is important in a book, journalistic article or website etc. It is not important on a multi-national forum.
So what? Everybody makes mistakes all the time. Even those who pride themselves on their spelling/grammar. I've noticed lots of mistakes on here by people. Most often it is by people using phones (very easy to hit the wrong key or have the predictive text mess it up). Or by people for whom English is not their mother tongue. For those who are English speakers from infancy, imagine how hard it is to think and to write in another language! Try putting your thoughts down in French, Spanish, Italian, German. If you're not bi-lingual, you will find it very difficult to do without making a mistake.
Then there's the slang, the differences between cultures, the writing styles and the differences in spelling between British English, American English and Australian English. As well as the dialectual differences within those.
Also, what if someone has dyslexia? They've had to battle with a learning difficulty that the rest of us don't even comprehend!
My conclusion is, it doesn't matter about spelling and grammar on this board. What matters is the thoughts that are produced and shared.