I believe each challenge is unique and post work may be simply stated with something like "generally accepted" or no note at all. For images which fit the "photo manipulation" genre, perhaps a note can be made by the poster to that affect. 

All in all, even if implemented, I believe the voters will choose the results based on how the image appears to fit the challenge and of course, image quality overall.

The portraits challenge did show one thing to me: Voters preferred the portrait to be human portrait, in the portrait sense, not family shot or animal.   Sure, some were postworked to emphasize the character of (and the person within) the photo.  This is done everyday both in digital and darkroom and causes no problems for me whatsoever.   

I am sure the suggestions will be considered but for the moment, I do believe the forum leaders are slammed.   Having worked with these folks over time, they do take suggestions seriously and must weigh the value against ability to implement without a full blown forum debate on the issues.

If others have thoughts on the post beginning this thread, please say so.

I am grateful for the challenges in the present forms and not at all unhappy with that.   We will see how it goes.

TomDart.