Yeah, that was the Maxi's favorite thing to talk about.
Early on, on the former PGC forums, when we were first playing, I discovered the online list there and would use it. My belief was that a lot of mafia members or role players would be checking to submit their night actions at that time of day. I think it may have helped a bit at first. I remember doing it a bit and it helping with my deductions but over time, since players could send in orders at any time of the day, it proved to be less valuable or I just found better methods. I know I'm always trying to eliminate advantages in the game too. By the time we made the switch to our current forums, I'd pretty much stopped checking it out since I really don't think there's any great info to get from it aside from maybe seeing that a user is sending a pm and that is a pretty broad action. Haven't bothered with it for years.
I think Maxi was just using it to hassle people. If he sent messages to people and saw them online but not responding to them or players online but not posting, then he'd pester them all about it. I think that was the bigger reason people started hiding their online status.