Better wash your brain about that implied misconception. Factor is much more like Lisp and Haskell (esp point-free style) than Forth. I guess "learn Lisp and/or Haskell and Factor won't seem so foreign" isn't terrific advice. But right now there doesn't exist many newbie guides at all.
I dunno, syntactically it resembles Forth quite a bit, what with : ; for defining words and () for comments and all that. Anyway, I have no problem whatsoever with high-level abstractions in Factor, nor with its concatenative nature, nor with its macros and so on. I know all these features from other languages. What I want is a just description of how these high-level things map to assembly, I guess. For example I just learned that: "Internally, a quotation is a pair, consisting of an array and a machine code entry point. The array stores the quotation's elements" - this is a kind of definition I want for all the abstractions in Factor. It's probably best to go through Slava Pestov blog and pick up such scattered descriptions, but I'd really appreciate if someone prepared a single article with all these definitions.
Note that the stack comments aren't actually comments in Factor - they're part of the function definition and are mandatory. The compiler will do a simple check to ensure that all of your stack inputs and outputs match up for each function call.