[Roger Cole]

But the same is true of gum bichromate, cyanotype and photogravure in comparison to silver gelatin methods.

Not really. All those involve chemically light sensitized materials, chemically converted to viewable forms. The sensitization and chemicals are different, but it's an inherently chemical process. It has no electricity used from outside (had to throw that in before someone started talking about ions and such.)

The idea that "digital is not a medium" seems absurd to me. Care to elaborate on why not?

But the problem with having it take its own direction and be distinct in artistic expression seems to be that it's essentially doing the same thing (the points above) as analog - using a lens to focus light from the physical world onto a sensitized (electronically in the case of digital) surface in order to record a visual rendering of that world. By necessity it's going to look more like analog than different. It is true that you can do a lot more and more extreme departures from a realistic rendering using digital methods. Extreme HDR that was mentioned is one, easily combining different elements into a scene that never actually existed in nature is another. That can be done in the darkroom but is difficult and limited compared to doing it in Photoshop. But any time these get too far removed from reality or at least the look of reality they seem to get dismissed as excess. Maybe that's the key and what's being discussed here. As long as it's not portrayed AS reality, along with all the mischief that could cause in certain contexts, there should be less complaint when digital artists combine elements in creative ways.