New account username- unable to use special characters, is this a bug?

[phil_dewar_fssi]

When setting up a new user account on 

https://www.splunk.com/page/sign_up

the Username field and FAQ say that you can enter your Email or Username.

But the field cannot contain @ or . characters hence cannot accept a valid email.

Example below with "a." being 'invalid'.

"NO $PECIAL C#RACTERS" 

You can enter underscores _

Is this inconsistency a bug?

Thanks, Phil