I agree with most of it except the last phrase of your ① which here I don't think it applies - people into conspiracies and alt-left/right/whatever are not such

I agree with most of it except the last phrase of your ① which here I don't think it applies - people into conspiracies and alt-left/right/whatever are not such a clearly delineated in-group and I think they're generally too sloppy to use subtle shibboleths. But here's an interesting paradox here, it's a kind of jargon but it's not for specialists. Kind of like an expert generalist's jargon. And the inner group is "everybody who knows enough to figure it out". A bit oxymoronic, like an "open-access secret-society". I'd guess that schizoid personality types may be attracted to dense and reference-rich language. And these very same types would be attracted to conspiracy theories due to their desire to belong, just as it's known they're attracted to esotericism. Overall I think the jargon and in-group signaling is real, but there's more to it, this compression-rich and high-connectivity thinking and communication mode is distinct, doesn't need to be about group signaling etc., and conspiracy theorists and other such groups are just what happens when this mode of thinking goes wrong, it's the pathological variation.