Ah-h-h-! An Honest man. One of the rules of firearm safety says, " Never point a gun at anything you don't want to destroy."
That particularly includes your own body. Blowing down the barrel puts that gun pointing where it should not point. It is a bad habit, which you will eventually learn when you get distracted by a friend or two while loading, and find yourself blowing down a loaded gunbarrel! It happens to most of us, so don't feel bad.
I stopped blowing down the barrel-- the way I was also taught --- when I decided that if I was going to teach kids Hunter Safety, and if I was going to paricipate in Shooting demontrations for the public, including kids, I had better adhere strictly to the same rules I was teaching in class. I never demanded that other members of my club do the same, but over the years, most have stopped blowing down the barrel, and use a slightly dampened cleaning patch with saliva to put out the embers, and clear the flash channel, nipple, or vent hole. There is a satisfaction in hearing air blowing out the nipple, or vent, loud enough to make a Whooshhing sound. And its nice to see all that smoke go out the barrel, even after the smoke stopped coming up and out the muzzle of the gun.
I know lots of shooters who will not blow down their barrels at the range, or when shooting in front of kids and adults who don't know much about guns or gun safety, but who will, when alone on a hunt, clear their barrel by blowing down the muzzle of the gun. Old Timers( like me ) will tell you that " IF you can't tell that your gun has fired, you should be shooting it in the first place!" We have a point. However, it is a point best made to knowledgeable ML shooters.
( Note: I also don't return my Ramrod to the ferrules under my barrel when I am hunting from a stand, unless I am sure that I hit my game, and I need to follow up and possibly finish the game off. I found I made less noise spooking deer after my shot, if my ramrod was already out of those metal pipes, and leaning against the tree I was standing next to. I put the jag end on the ground, so that I have to lift the RR vertically to bring the jag to a patch on my muzzle and then run the patch down the barrel, Hand over Hand, in slow movements, to clear the barrel for the next powder charge and PRB.I can hide vertical movement behind the tree trunk. The clatter of the stick coming through the pipes, and the whipping motion of the stick being turned upside down is motion that a deer can see, and since it is a fast motion, they will become alarmed, and run. )