I still can say that "Anonymous" username it is "tysat" click on last edit topic and will see it.
I guess it's a different user and based on this, tysat is most likely a moderator at that time, that's why he can edit other users posts. There's so many old users become a moderators e.g. blitz, badbear etc as I read on the old topics before.
Tysat would have been a moderator around that time if I remember correctly,