[carpeperdiem]

I just verified that my store, upgraded from 4.1.3 through every revision to 4.1.8 WORKS AS EXPECTED -- I have "disable anonymous checkout" unchecked, and the "*" next to the username and password fields are NOT visible, AND when the customer proceeds through checkout, if the username and password are left empty, as expected - the transaction is just fine.

There must be something with your store -- my live store and my test stores both work as expected on 2 browsers (IE & FF) and 2 operating systems (mac/winxp-pro)