What is particularly worrying about this, is that it means they are storing passwords in clear text, so the user account database can be hacked.
Normally when you enter a password, it is encrypted by a one way hashing, so there's no way to get the password from the hashed version, which is then stored.
When you enter a password, they hash it, and then compare it to what's stored, and if they match, you're in.
However in order to append the 6 digit code to the end, they must be storing it in clear text. Very bad practice indeed these days.
Also, it's really not intuitive, why can't the instructions say to enter "password"+"code" in the password field.
Finally, this 2FA approach they've chosen, unlike google, means that for example to access this discussion board on a PC, I had to fire up my Mac Mini and wait for it to boot, and do all it's stuff so that I could get a code just to access the site. It needs to be offered via email too!
All in all, a really poor user experience, and hours of frustration with a company that's supposed to be easy to use!