XenForo has an addon that nails anyone trying to have two identities. View attachment 4484
Not sure what that means...but other have too...when they are found out I think they get banned.
For the longest time our friend epostle1 had that, also went by the name epostle without the 1 , which I think he is now, and another name starting with K..like Kapha or something.
He got locked out under one name...depending on which search engine he was using ,so he had a user name for each search engine!:) In the end he had to pick one...and meld them together.
So no...there is nothing that 'stops it' being done...except when the admin catches it being done.