This is how I replicated it:
With one computer logged out, I clicked on a member's profile. A split second later, while on the "who's online" list, I refreshed. When done just right, the list appears as it does above. It is a bit hard to replicate; I only managed to do it on my first try (luckily). I wasn't able to get it again.
Basically, I'm not able to see the profile as a guest, but "Who's Online" sometimes says that I can.
I believe this also explains a weird message that appears occasionally on the "Who's Online" list. Once in a while, it'll tell me that a specific member is logging on. However, when typing info in, the compy has no clue who you are, and there's no screen between logging in and arriving at the board index.