An imported ban from one of our old banned_user.cfg it seems.
I think there is no way to trace who actually banned you.
Also, it's possible that someone banned you from one of our other servers because if you get banned on e.g. Hidden or TF2, you will be banned from all of our servers because we use SourceBans.
Unless anyone knows who banned him and why he was banned, I say yes for an unban.