To put it that into context, some tags count as upvotes, others count as downvotes, "Troll" is a downvote. So to have your post labelled as "Troll" with a positive score, it has to have enough upvotes to compensate the penalty from the "Troll" votes, but without having another tag dominate. 5 is the maximum score.
"Score: 5, Troll" is therefore the mark of a very successful troll.