Any combustion in which the fuel-oxygen ratio is as uncontrolled, as it is in the likes of a spirit burning stove such as a trangia, is never going to result in 100% combustion of the volatiles.
This is a result of among other things the fact that the unburnt products are able to escape, along with the loss of heat to the surrounding surfaces and environment, and as you say Graham O through light. So there will always be an amount of soot produced.
Smokey fires though are hotter, this is fact. The soot particles increase the radiant heat surface area of the flame. It is often problematic particulary when dealing with fossil fuel fires as seen recently at the Buncefield fuel depot. The majority of the fire fighting resources were directed towards cooling the flames so that the fire base can be reached and so the radiant heat did not cause the surrounding tanks etc to ignite.