Originally Posted by Obsi
a couple of us were around when the log house and firepit were being built, and were expecting the whole thing to burn down (it didn't).... and we even tried walking into the firepit and then standing next to a wall to see if we would burn it down - and it didn't - so I don't know if it's a random thing then or not...
Exactly, I was there then, as we were concerned someone walking too close could cause a fire to spread after we'd removed the fire wall which had been build just in case. I've also failed to light trees on fire while accidentally setting myself on fire whilst trying to burn zombies.
There's apparently first hand knowledge for both positions, however given the range that a fire can jump (up to 3 blocks) then examples of fire spreading by someone who's not obviously alight may instead be the fire jumping - remember it's 3D, so not just Nth/Sth/East/West but also vertically.
Other than that it could be something that's a bit bugged and can be spread sometimes, but not others. I've not researched it too much on forums etc myself.