In this answer, which was written under my account on Super User and ported to Web Applications, I was able to upvote two of my comments.
On other pages, I am not able to reproduce it, only in this page.
Logged in as:
You are up-voting an anonymous user with your username because you registered with Web Applications (2013-06-10 13:05:19Z) after the migration (2013-06-10 13:00:52Z).
Comments aren't given the same priority for user association during migration