Salem

What happens when an obstacle is between a Torch Post and a raider, e.g a Mine Entrance, a Farmhouse, ...? Will it still attack the raider?

Emmm rather yes, if shooting avoid walls xD

torchposts/braziers are not deterred by walls or other obstacles (e.g. cliffs). However, they are unable to shoot people in other worlds (e.g. when entering your house, the culprit will be relatively safe, aside from the base trespassing drain).