While the versatility seems nice on paper, I disagree for several reasons.

1) I cannot readily think of a situation in which I could not find a better use for the candle. It may be because I'm in a northern area(pennsylvania) and deal with relatively cold winters.
2) Seriously, if you can't find something better to eat, you've got issues. I mean, you've got to figure if you have your priorities straight, that you've got a week to figure out how to get some food.. whereas you have only a few hours before you freeze to death.
3) Beeswax is edible too. Unfortunately it really doesn't digest very well. I suspect tallow has the same effect. Anything waxy doesn't seem to digest very well. I'd reckon the beeswax would taste better though.
4) If your knife was edible, would you eat it? Honestly.... only if I was completely paralyzed and unable to *edit* use it. The purpose of that analogy is to relate that tools are designed as tools - they serve better function in their intended role. If you're smart about it, you'd never even have to consider something along those lines. I'd be using the candle to readily start fires to keep me warm so I could try to think of something more realistic to eat. Such as small game, grubs, plants, whatever. The last thing on my mind would be "MMMM.... candle.... *drool*."

I had no idea rhubarb leaves contained a poison. But then again, I don't go making rhubarb because I heard it tastes awful. Live and learn. Not to derail my own thread but does boiling the leaves destroy the poison?