[Sparkologist]

Listen to your uncle Less.

As I understand it, the plus sign appears next to a name if you are on their buddy list. So if you saw your name with a "+" next to it, I am guessing that you saw it on another person's computer, and they have you ticked as a buddy.
For example, I am on lettie's buddy list, (I can't think why )... so my name appears embelished with a "+" when she is logged on but not next to my name when I am logged on.

Conversely, the ignore list just hides a member of that select band from view, so that you don't see any of their posts. Some of the threads get more than a little surreal when you try to make sense of the conversation when half of it is missing.