I did some minor changes to wicket example authentication3. I put the SignInPanel on the HomePage. The changes look like this:
Now you can see the SignInPanel on the HomePage. If you login you are redirected to the home page again. Everything seems to be fine. But if you click the Admin Page link you are redirected to the login page. I think you should end-up on the Admin Page itself because the login was correct.
That means also, you cannot use the SignInPanel on your application's home page for user login.