Great discussion!
I'm interested in the way it has become, in part, preoccupied with authenticity; I didn't understand that concept to have anything to do with the original question, but it is very much in the background. (and slightly out of focus😀). It struck me, reading this, that one of the concerns regarding authenticity, here, is being expressed as a desire to differentiate between simulation and dissimulation -- some of the responses seem to want to identify the practice of digital post-processing as a kind of simulation, which, according to some philosophical and theological traditions, is an act of deception, an abuse of good faith on the part of the photographer (granted, most of these historical discussions (the Wikipedia entry on "Dissimulation" links to a few) pertain to the self, not to the production of expressive material).
Dissimulation, on the other hand, seems potentially to bother people more, because what it leaves unspoken can lead to a misunderstanding or a misreading located in the viewer.
What's the difference? Well, none if the concern is a fixed, aesthetic one -- if as mabelsound and leicasnapper argue every decision we make about images (film type, speed, color filters, traditional processing, digital post-processing) are basically parallel kinds of decisions. In this regard, every photographer is a kind of simulator, and everyone understands this.
But it's that concern, I think, that everyone does not understand it -- that concern that audiences might reasonably expect that what they think is photography simply is the result of light and film and chemicals -- that leads to the reading of dpp as a kind of dissimulation (should those images actually wind up in a gallery, for example).
Here's where I'll express an opinion: I think this second concern -- expressed by those, in other words, most opposed to mabelsound's assertions -- comes from the old tradition of defending photography as a 'legitimate' expressive and artistic process involving decision and action on the part of the artist. When someone here referred to digital plugins as "another tool in my kit," he or she struck a chord: can proprietary "tools" -- especially if you're not a programmer who understands them -- be a legitimate part of expressive photography? But this leads inevitably to: can proprietary chemical formulations and film -- especially if you're not a chemist who understands them -- be a legitimate part of expressive photography? Sure, right?
I'm not at all interested in Photoshop or its plugins, personally, because I so much enjoy the physical stuff (and when I do venture into the virtual, I prefer the -- admittedly limited, by contrast -- GIMP for its openness). But on the issue of authenticity, I'm with mabelsound.
If you've actually read all of this, accept my apologies for taking so much space and time simply to say: "I agree with that one!"
