If you are hiking or carrying the stove in such a way that it cannot be carried upright, then use the supplied wrench to remove the burner assembly and replace it with the brass cap, and tighten the bleed valve on the filler cap. Store the burner unit in a Zip Lock bag or similar to keep the inside clean. It only takes a couple of minutes to perform this procedure, so it isn't time consuming or difficult if you let the stove cool for a few minutes first. Those were put there to alert you to avoid potential problems. The stove comes with a jet cleaner in case the jet becomes clogged.
Alcohol burns very hot, without much of a visible flame and produces almost no soot.
In an emergency you could preheat using kerosene in the alcohol preheat cup, but expect it to leave a soot deposit on the burner and require several cups of fuel to achieve adequate preheating. It burns without noticeable fumes, and because it burns kerosene it does not produce excessive carbon monoxide as do gasoline stoves. It isn't as loud as a Coleman stove or lantern, but you can hear the mild roar of the burner unit in operation, just as you can with a Primus kerosene stove. You've seen my web site. You know I have a half dozen different models of single burner kerosene stoves.