I agree that EY is probably overconfident in MWI, although I'm uniformed about QM so I can't say much with confidence. I don't think it's accurate to damn all of Less Wrong because of this. For example, this post questioning the sequence was voted up highly.
I don't think EY claims to have any original insights pointing to MWI. I think he's just claiming that the state of the evidence in physics is such that MWI is obviously correct, and this is evidence as to the irrationality of physicists. I'm not too sure about this myself.
As for why SI's approach is dangerous, I think Holden put it well in the most upvoted post on the site.
Well there have been responses to that point (here's one). I wish you'd be a bit more self-skeptical and actually engage with that (ongoing) debate instead of summarizing your view on it and dismissing LW because it largely disagrees with your view.
It seems a bit bizarre to say I've dismissed LessWrong given how much time I've spent here lately.
I have several questions related to this:
If you visit any Less Wrong page for the first time in a cookies-free browsing mode, you'll see this message for new users:
Here are the worst violators I see on that about page:
And on the sequences page:
This seems obviously false to me.
These may not seem like cultish statements to you, but keep in mind that you are one of the ones who decided to stick around. The typical mind fallacy may be at work. Clearly there is some population that thinks Less Wrong seems cultish, as evidenced by Google's autocomplete, and these look like good candidates for things that makes them think this.
We can fix this stuff easily, since they're both wiki pages, but I thought they were examples worth discussing.
In general, I think we could stand more community effort being put into improving our about page, which you can do now here. It's not that visible to veteran users, but it is very visible to newcomers. Note that it looks as though you'll have to click the little "Force reload from wiki" button on the about page itself for your changes to be published.