Whoops! I guess I'm too late.
Firstly, this a nicely laid out page, up to your usual high level.
Now I'll be blunt...part of this history confused the crap outta me.
a) from the position of the handle "beak", and appearance of the blade, the kopesh appears to be upside down with respect to the other blades. And the outside of the curve seems the sharp bit. If so, it seems a big stretch, almost disingenuous to relate it to the khuk. Particularly since so many other blades have curvature opposite to khuks like that the kopesch appears to have.
b) the depicted kora, notably also from Nepal, is not mentioned even though the inner edge of the curve is sharpened (as I understand it), and would appear a much closer relative.
The similarity of the kopis is, of course, readily apparent.
The rest of it seems fine to me, apart from appearing on my browser as narrow column ALL the way down the page, and thus a little annoying to read.