Comment 32 for bug 895885

I didn't take a look into the coding, so I don't know for sure, but if the list AlexB mentioned is the same list the game checks to see if the player has any buildings left, then making buildings with Insignificant=yes added to that list would make having the tag almost pointless. After all, the purpose of it is that the building will NOT be in that list, so it won't count as a player-owned object.