You will, however, be judged by the quality of your writing. So spelling and grammar do count. If you're spending a lot of time on the net and you're shaky in these areas, it's worth brushing up on them. A side benefit is that taking courses involves meeting people you can actually see. Know what you're talking about and make sense Pay attention to the content of your writing.
Bad information propagates like wildfire on the net.
In addition, make sure your notes are clear and logical. It's perfectly possible to write a paragraph that contains no errors in grammar or spelling, but still makes no sense whatsoever. This is most likely to happen when you're trying to impress someone by using a lot of long words that you don't really understand yourself. It's better to keep it simple. Don't post flame-bait Finally, be pleasant and polite.