the L bot allows designated users to retain control of the channel, preventing random users from taking over the chatroom. (setting a passkey, kicking people, etc)
The bot left because it had not been used by anyone to gain operator privileges for a period of 44 days.
The reason for this is that I think the only valid user on it was Neverdown, who I haven't seen for a while.
If other users were also set up on it then we'd still be able to use it, but right now noone has operator rights at all. That won't change until everyone leaves and comes back in.