Hmm, I was responding to the third post (by an anonymous) in the "Sign-ups?" thread. I wasn't paying attention and clicked edit to his post rather than respond. I typed my post up and submitted... and it edited his post with what I typed o_O I restored it (thankfully I had it open in another tab too) and posted my reply correctly, but I'm surprised I was able to edit it.
I guess I just wanted to make sure if this was a mistake or not, because hopefully not anyone can just rewrite anyone else's posts, heh.
Updated