A troll bridge, in fairy-tale usage, is an ordinary bridge which trolls hide under, uttering nastiness and threats when others cross it. The revisionist Wikipedia version, intended to attempt to reform trolls and prevent troll war and flame war, is to find an article that both sides of the war can work on without their usual level of rancor, and come to agree on facts, dates, and other neutral information, thus "bridging" their differences. This is a good distraction from more theoretical or abstract or political material where they might not agree.
Finding such bridges is one way to overcome a political dispute.
The more ornery trolls can be enticed with the potential to utter more nastiness and threats, and then surprised that everyone else is cooperating given lack of an issue to truly disagree on.