Lorin David Schultz wrote:

I've tried working this through in my head, and either it's just too
early in the morning or I'm just too stupid to figure it out.

"Typical" impedance for a line-level input is around 20K or so. A
device I'm looking at has combo Line/DI inputs. The switch changes
input sensitivity but not impedance. Thus the line inputs are balanced
+4, but with an input impedance of 10 Megohms. What are the
consequences of such a high input impedance (if any)?

None you need to worry about from the perspective of plugging it in and
using it.

That's an unusually high impedance. What's the unit ?

Graham