Stack Exchange network consists of 177 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
I just ran across this user name which is a clear advertisement for a service...
Is this allowed here on AU?
Yes, I found this already...
Using a domain name as your nick won't actually link anybody anywhere other than your profile. It won't attract Google rank or any other benefit.
And in this case it looks like they've already change it by their own volition.