This is a great video. A summary for those who don't want to wade through it:
The main message is that if the knot is slightly loose, or messy, the strands pinch unevenly in a fall, and it can be really hard to untie (depending on the rope). Most of the video is experiments to show that. The knot only had to be slightly loose to cause problems.
The part that surprised me is that there are two different ways to tie the knot that basically look the same. They only differ in which of the two outgoing strands is the one that's loaded. They're both perfectly safe, but one can be a lot harder to untie than the other after a fall. I actually find it hard to end up with the "wrong" version of the knot, but I might just be lucky with what my muscle memory has latched on to. I certainly wasn't taught to watch out for the difference.
Interesting to see a completely custom renderer. Look at the page through dev tools inspector - it's just a single canvas inside body. Everything is drawn using the Canvas API. Not even WebGl, just a regular old 2d context, bunch of fillRect's and drawImage's.
And then you accidentally refresh or close the tab and everything is gone. I usually use specific requests over many days if I'm reverse engineering something so having these available, sorted in folders for me is important. Of course for other uses cases it might be fine to have them live in the browser.
