Daniel and I have found that the optical lever sign convention for ETMs and ITMs was changed in May/2013, and now it's opposite of what I remember.
I'd like to know why it is/was a good idea.
Right now, the dot on the screen goes up when the OL beam goes down.
It probably was changed so that the convention matches the SUS coordinate system so that positive pitch in the OSEMS should read positive pitch in the OLs, if this isn't the case then it's an error.