Found a couple resources that (briefly) describe the I-cord bindoff I will have to do sometime on my shawl (that is Esther Bozak's Trinity Stitch Shawl):

The Blueberry Bed Jacket pattern by Mary J. Saunders(a neat pattern, also talks about the bind-off in the section on the sleeves)

the Shaped Shawl, at Woolworks, by Carry W. Croghan also has a description of the bind-off.

It is, as I expected, a situation where you knit I-cord but do a k-2-tog with one of the "live" stitches to bind it off. We'll see how it looks. I suspect it's a PITA to do, but if it gives a nice firm non-floppy edge, then it will be worth it.

I have also decided that when I reference a free pattern on the internet or a published pattern, I will strive to (as much as memory and given-attributions allow) give the name of the designer. Especially for the free patterns, because all those designers get is the warm feeling of people using and enjoying something they figured out.