Okay, this is weirder and weirder. I found waterwren, but she was banned a long time ago. She was last active in 2008, in fact. I've never seen a glitch like this before. Even if you did log in as her, it wouldn't have let you post as her, because she's banned. When I look at the thread in question, I don't see any posts by waterwren, just snowdragon, and when Dotty quoted "Waterwren", the quote showed up (for me) as not being attributed to anyone. I had to scroll up and find that it says SnowDragon made the original quote.
So, very very strange. But I'm going to go with "Forum Glitch" or "Gremlin"