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I logged into the client a a few times over the course of the night, and multiple times when I logged in (and also when I exited the game), I was prompted with a "(person) has requested you to be their friend, would you like to accept?" confirmation box. However, I had already accepted these people as my friends and they were already on my friend list.
In some instances the person was duplicated on my friend list after I again accepted the "request."
Finally, I invited one of my friends (who was a duplicate) to join a game, and when they accepted and joined, it was actually a different person from who I invited (i.e. the name I invited was Sam, but it would seem the invite was actually sent to Paul, who was also on my friend list).