That private message was part of a new feature to encourage wiki participation, by helping existing Less Wrong users onto wiki accounts. Unfortunately the link to create an account didn't point to the right place.
If you tried to create a wiki account and had the brief flash of "submitting" (like Pfft), make sure you've got a validated email address associated with your account.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.