I was browsing the "Who is Online" page a bit ago, when I noticed that one guest's location was "Posting a message". Is that message a bug, or is guest posting allowed somewhere?
Oh, this was on the SE side of the forum, if that makes a difference.
That would've been my second guess, but I thought that if you weren't logged in and hit the post reply button then it redirected you to the login page. But then I don't know how the user tracker is coded so for all I know it could still register you as Guest - Posting and Message in that circumstance.
For the bot it goes Viewing topic -> Posting. It waits a little bit, and then goes to logging in.