I remember reading some mod saying they liked to be on invisible so that when someone starts trolling or just generally being a dick, the mod can delete their posts and they get all freaked out not knowing who it is which I thought was funny
I just do it cos I often keep bl open in the background all day while I'm doing other stuff, and don't really want it to look like it's all I do with my time
Well, if you go on as Appear Offline you can then suss out who is on before people get the chance to send messages. If necessary, you can block people before going online. :D
Truth is, there was one person who used to message me constantly whenever I jumped online on BL and I never got around to changing it back to visible once it was resolved. Now I've become a little attached to my invisible status. Kind of like a cloak that allows you to do really cool shit (or perhaps I've just been thinking too much about Harry Potter)