What is Reddit's opinion of The Mountain Guide Manual: The Comprehensive Reference--From Belaying to Rope Systems and Self-Rescue?
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I have a hard time spelling it correctly myself, that's why I noticed, haha.

Yeah true, Youtube videos are often awful, I don't think I would recommend learning from them. I think the trick is figuring out if the person you're learning from is actually safe or not in general and then deciding if their practices work for you. Like you said though, sometimes you end up on a climb with someone and then you realize they might be sketch, that's not a good feeling.

Since you mention guide standards, you might find something useful in this book, I don't think you mentioned it in your initial post.

https://www.amazon.com/Mountain-Guide-Manual-Comprehensive-Reference/dp/1493025147

Looks like it could cover a lot of the content you're looking for.

And again, I was just fooling around. I'm always stoked when people are getting after multipitch stuff, I think it's what climbing is really all about.