I fixed the bug and test with LOCAL user already. It looks like this now when you try to register the same user twice:
Basically I:
remove the html tag from Messages.properties file
insert the html tag again with jQuery code in eureka.registration.js file
Nothing change on JSP page and Servlet page
If you think the UI looks good, I will pull a request.
After pushing submit, says: Account already exists! You may go ahead and login.