There are a lot of people out there who are barely literate; although for obvious reasons probably not so many of them make it to HN. If someone don't know how to spell and needs to communicate in a latin script they have a couple of chances. Sounding things out, guessing at spellings for words that have only been heard, etc.
The idea is interesting and worth exploring; but ultimately I'd worry that it will be exclusionary and hard to work with for people who don't do much written communicating.