Is it okay for oil to smoke in stir-fry? I've always been taught that when frying anything at all, it's of the utmost importance keep the oil below its smoke point. Once the oil starts smoking, I've heard, it's game over-- the oil is denatured and everything in it will have its flavor ruined. And, from limited experience pan frying and deep frying things (I'm still working on the basics), I've seen that this is true. Once the temperature climbs too high, the oil starts to stink and the food ends up tasting like rancid oil.

But, when I watch stir-fry video tutorials, there's almost always smoke. Not just a little bit, either-- it looks like they're thoroughly burning their oil. For example, here's Chef Hiroyuki Terada making chicken fried rice: https://www.youtube.com/watch?v=UzbRwICWODk (he adds the oil to his wok at 3:45). I have no doubt that Hiro knows how to make a delicious stir-fry, but would it be better if he didn't let the oil smoke? Is the high temperature more important than the integrity of the oil? Or, am I completely missing something, and the oil isn't being denatured at all?
Yes, there's smoke coming off the oil, but it's not heavy, black smoke.

If you're frying things, when I see that, it's a sign to either get the pan off the heat, or to get food into the pan to cool it down.

When you're stir-frying, you want very high heat, so you're often working right at the smoke point.  Whereas, for sautéing, I always learned to put the food in when it shimmers, but before it starts to smoke.

So, should you let the oil smoke?  Generally, no, but it's okay if you use it as an indicator for when to put in food if you're quick about it.

update: To answer the culinary questions in your comment : 


The oil does denature, but it's not all denaturing at once, just like when you boil water, it doesn't all evaporate at once.  Or if you burn an item, the whole thing doesn't instantly turn to ash.  It's not a boolean (yes/no) answer, it's a question of the degree to which it's denatured. Letting it smoke so you know when to put in the food isn't the same as if you let it sit there an smoke for 5 minutes because you don't have your food ready.
Moist food will cool off the oil because the water will turn to steam, resulting in evaporative cooling.  This process ends up sucking energy (heat) out of the oil in the process.  Flipping the food repeatedly (as you would with a sauté and some people do with a stirfry) can also cool down the pan, as you have more heat transfering to the air (more surface exposed while it's being flipped), and you typically lift the pan off the burner so there isn't as much new heat entering the system.