This concept of a Troll
generally only applies to forum boards.
Essentially it is a person who decides to Troll, but with abnormal intentions of only posting to help. Thus, they are almost complete opposites of Trolls.
This person will post anywhere in the Forum as many times as they think they need to get their opinion/point across. They tend to have 10x the post count of normal active forumers.
Most of them become Mods, well known through out the community, and are most definitely never banned.