Kinda gross to think about, but it's just wicking (literally!) out the wax from one's ear canal and using it for fuel. I'd have to think that it's safer than dumping lots of chemicals in there in an attempt to flush it out.
Except that in the Quackwatch link, it was established that
1. the process does not actually create the negative pressure required to draw the wax up against gravity,
2. The was on the plate that is allegedly from your ear is really from the candle, and that
3. 10% of ENTs surveyed had seen patients who had been harmed by candling (mostly burns).
I call bullsh!t. There are plenty of alternative medicines and procedures that have effectiveness, but this has not been proven to be one of them.