There's a part of me thinking that if one is going to insist on a total lack of postwork as an absolute requirement for worth of a digital piece, then you also have to specify the hardware, operating system and monitor settings that the viewer needs to use. It's the only way be completely certain that the viewer sees exactly what was spat out by the render software.
Artistic worth has absolutely nothing to do with the process used to create it, except in so far as the execution of the process reflects the artist's skill and enhances the impact of the final result. Meh, not trying to sound clever with all the long words, sorry. Just saying that zero postwork restricts the tools available to the artist, places some effects beyond the reach of many digital artists, and gives greater influence to technical skill than to artistic flare and creativity. A valid exercise to demonstrate technical skill but not the sum total of artistic worth. You use whatever you have and can use to create the result you want. That's been the case for artists since people painted on cave walls. ("What? I can only use a straw to blow paint, I'm not allowed to use my fingers to smear it around afterwards?").
I usually have an end result in mind; Poser (my usual 3d output software of choice) is just one tool in my toolbox. I'll use whatever tools I think will produce the final result I have in mind, be that a camera, PSP or Photoshop, even a scanner and fabric/paper/autumn leaves/leather/dog nose-art*
*Dog nose-art: what a dog leaves on a window. My windows are not dirty, I am a proud dog parent showing off his work!
I'll totally agree with comments on promotional art, in that some renders ought to be unretouched, and any postwork (including compositing) ought to be described. I think it's okay to postwork in a non-distracting background such as a plain colour or gradient fill, though. Promotional art is primarily illustrative, and only secondarily artistic. It's main purpose is to show people what comes in the box.
Soooo... is this thread also a place for talking about postwork techniques?