Totally Ridiculous....Auditions on YouTube!

A difference is a difference no matter how bad the room or acoustics are. You might not hear a component or speaker perform at its potential, but if you can hear an improvement (or the other way) when something is swapped out, then it exists.

Completely agree.

Certainly not audition quality but of course you can ascertain qualitative differences in well-recorded YouTube video. If you can’t, there’s an issue with your aural apparatus and cognitive interpolation, and you shouldn’t be in hi-fi.

You can hear a difference on YouTube, especially if it's a big difference. I was watching Mr. Carlson's lab and I could definitely hear a difference when he switched microphones. He always used a good microphone, but when he switched to a high quality tube microphone it sounded much better.