Hello, I'm the creator of LIGH, DEST, EMP elements.
There aren't any changes in burning system since TPT starting. Burning and fire temperature is very low, top flame part have same temp (it must have higher). Coal can't be snuff outed by water, WOOD burns over fast and stable, fire really cold for this game and even can be used for cooling. Some people could get from this game wrong notions that metal can't be melted by fire and think that metallurgy is something supernatural. I think, we must reform burning system. You say 'it breakes saves', yes, a few ones, but can it be an option? Breaking by pressure makes not nice square lines, we also can smooth this with random (but I'm not about grid step deseracing). What do you think about this? I can realise this first.
2021 edit: This post is definitely silly because stuff like that is too advanced for TPT
In real life, humans have been able to melt various forms of metal by burning stuff (presumably coal or firewood, or derivatives such as charcoal or coke) for several thousand years, so I see no reason for that to be impossible in Powder Toy.
In TPT, the melting point of METL is 1000 C.
http://en.wikipedia.org/wiki/Fire#Typical_temperatures_of_fires_and_flames
"carbonated water is the only water that can put out coal fires"
I can't immediately think of any chemical or physical reason why this should be the case. Perhaps you could link to some evidence of this?