I've never bought any of that bank line, but I looked it on on those Amazon links and very well may have to buy some!

Just looking at the picture of it, reading about the tar, reading about the stiffness, and letting my imagination run wild - I'm assuming that knots tied with it should probably be considered permanent. Is that true? I would think that once the stiff cord "kinked" into place in a knot, and the tarring took hold, there's no way you'd be able to untie it. But it's difficult to know for sure without ever having touched or seen the stuff in person.

Paracord varies in how easy it is to untie for me. Something like a tautline hitch usually unties easily, but other knots - especially if they get wet and are under heavy load - are darn near "permanent" in paracord.