I hate when someone signs on to their messenger client under invisible status.
I don't talk to people often. I'm not a very chatty person. But when I do have something to say, I'd prefer to know whether or not the person is available to say it to.
I don't understand why you want to sign on as invisible. Why bother signing on at all if you don't want people to talk to you? If you have a specific person you are trying to avoid, why is that person on your friends list? Make that specific person unable to see your online status, or block them, and stop being such a coward.
Invisible people suck.