Unable register new user at password-restore page

User try to register at password-restore page:
1. open forum,
2. click 'Sign in'
3. click 'Forgot password'
4. click 'Sign up'
5. fill fields with valid data(email = 'e589759@rtrtr.com') and click 'ok'

User'd expect successful registration, but valid email is not valid.

see video for detail.