Mute I think it's harsh to say that they shouldn't write in English at all. However, this is why you should ask help from editors and proofreaders. It's nice to have another set of eyes looking after your work after all. People shouldn't let "I can't write in English" be an excuse not to write, because guess what? You'll be surprised by how native speakers aren't familiar with their own grammar and spelling rules.
If anything else though, I hope there is an option to let users write in a language they're comfortable with. Regardless of language, I think typos and grammatical errors will still exist.