Yeah, I agree — I really doubt it's that large of a shift, as I mentioned under "Specific language effects." I find it hard to believe that JavaScript could really be less expressive than C and assembly.
I also found it interesting that Objective-J is well ahead of Objective-C. The parts of those languages that are not pure Javascript and C, respectively, seem like they should be equally expressive. Especially when Javascript and C score side by side, eliminating any effects by expressiveness of the subset language.
I think one point that has been overlooked so far is that many projects might copy in a bunch of JavaScript (jQuery, etc.) and then write the glue code in CoffeeScript. So you get a commit with 3kloc JavaScript and maybe 20loc CoffeeScript.
