I'm not a Bungie Employee, but I had a similar thing happen to me way back when, a friend and I was playing a strike and our usernames in the little ticker feed did not correspond to our actual usernames, they were some other random people's names. It hasn't happened since then, so we wrote it off as an obscure and transient issue. Hopefully Bungie will be able to investigate, thanks for your report. You may want to consider adding #Gameplay, that will help the right people investigate :)