Keep this in mind:
f=Forward
d=Down
b=Back
u=Up
n=Neutral(don't put in any commands for a split second)
Any command conjoined with a '/' is the mix of the two commands on it's either side.
E.g. d/f refers to the South-East direction.

Simply said, the Korean Backdash Cancel can be reduced to:
b, n, b, d/b, n, b and now you can repeat d/b, n, b forever.

Try it!

"What? You couldn't do it even after knowing the exact commands?
You must be a total noob."

That words would be very routine if you can't do it.
But I shall tell you why you can't do it.

You can't do it because the commands aren't correct. Yes, they aren't correct.
They won't make you do the KBC('K'orean 'B'ackdash 'C'ancel) or any of the back-dash cancels(BDC).

Say this out loud:
"A back-dash will only be executed when there are two consecutive b commands in the command history"

Repeat with me

"A back-dash will only be executed when there are two consecutive b commands in the command history"

(Command history is just a sleek little tool that shows whatever you input during practice mode. Try finding this tool in the practice pause menu)

You can quote me on that. There is absolutely no other way you can perform a back-dash without pushing b twice(assuming you are on a D-pad).

So by this logic, there should NOT be a second back-dash executed as soon as you press b only once after the first back-dash cancel(Back-dash cancel= b, n, b, X; where X is any movement button).

But the pro-players claim to do it, nevertheless it is impossible.

How?

Because the real command is something else.

There are two correct ways.

However, one method is clearer, but the other one does no harm.
I shall replace all commas with vertical bars like this--> '|'. It makes the text look more friendly to the eyes.

First, the clearer one is:-

b | b | n | { d/b | b } | b and now repeat b | d/b | b till your fingers die, well if you want them to.

You see that b command in bold formatting? Yes, that's the correction that everyone is missing out on. You will also see two squiggly brackets in there. Those just mean that the commands inside those squiggly brackets is to be done as fast as you can but NOT at the same time.

Secondly, the easier version but a bit messy is this one:-

b | b | { b | d/b | b } and now repeat the entire command excluding the first two b inputs.

The extra b command inside the square brackets is often an input mistake. You can afford to do it like this because it does no harm.

Do you see why this will work?

The correct version has two pairs of two consecutive b commands. Thus, the rule that I taught you in the previous section works here to facilitate this trick. That's why you get two back-dashes in a row without delay.

So do you see why this is often misrepresented?

If you didn't notice, what happening here is that the advanced players don't input just d/b and then input a single b (after a BDC) to double back-dash quickly, they are actually doing any one of the two correct versions as an input mistake.

It's not really a mistake because they are still doing what they intended to do, but it should help all the newcomers out there or even people who never knew about this.

Cheers,
Seriously0Serious