Ditto. I googled around and the gist of candle physics is this: -wick is lit and then heat travels downward to the candle -immediately begins melting the wax, which are hydrocarbons that fuel the fire. it's a simple combustion reaction as they mix with oxygen in the high heat -capillary action sends melted hydrocarbons up the wick, continuing the reaction

No mention of energy loss when lighting another candle... but really heat is the byproduct of the combustion reaction, so lighting another candle is harnessing the byproduct and doesn't interfering the reaction. The expression is valid! :-P

http://www.explainthatstuff.com/candles.html

http://candles.org/candle-science/