It seems simple, but this little fix would drastically improve online games. Almost every game I play online ends the same way, a griefer finds base, burns it down, and everyone quits. If the option to "light" was removed from player made structures, griefers would have to work that much harder to burn down what everyone else has built. This would also lead to less accidental burning of structures, which would be a huge help in online coop games where new players pop in and out.
Griefers are far too common for the torch to be as powerful as it is for destroying structures. Nerfing the torch is not a permenant solution, as a griefer will still be able to plant trees or drop items to start a fire, but at least it's a start. Forcing a griefer to chop down some trees before starting an inferno might thin the herd of trolls slightly. A heavier handed fix that might actually solve the problem, would be to remove the "light" option from the torch and lighter altogether, and add in a much harder to craft flamethrower for those who must ruin the game for everyone else.
As it stands, players keep their base hidden from pyromaniacs, and a fog of distrust prevents jolly cooperation, to no avail as base will undoubtedly be burnt down eventually. Please do something Klei, anything really.