Hello,

It's far more easy than that: I tried my steps on oxwall.org and I had the same result!

I used firefox but I guess it could work with chrome and maybe others as well

To make it short:
- you have an account on the site
- make sure you saved your password into browser and can sign in without re-typing your password
- log out (you may clear session if you want it doesn't matter)
- try to create a new account
- it wont work

Thanks Regis, we followed your steps and reproduced that. We reported the issue to our developers. 

Great :)