I understand your personal preference on the matter, as a photomanipulation may cover up the original parts of the creation - which could lead to the viewer being shocked as the appearannce differs from the primary source.

However, Just like any matter, there are a variation of pros and cons on the subject...

Just to clarify my speculation:

Just like any adaptation, people perform these edits to improve the quality of their submission. Whenever you assemble a creation, the purpose is always to improve the appearance. 

Example B: A submission with no formatting, straight up vanilla minecraft with no fancy shaders or any mod to improve the appearance. You see what you see, you get what you get! Its what it is on the tin...

Example A: A submission with formatting, a variation of mods that improve the appearance of the submission, Including shaders, optifine and so on... 

Heres the comparion: http://imgur.com/r2Ao4GX
 (Created especially for you)

Now then, Imagine both was on the popular reel. Ask yourself this, which one would you view first or at all for that matter. I gurantee 65% of the community would view "Example A", as it contains a higher quality and its presented perfectly and in all honestly looks much better.

Furthermore, you stated.... "But I see so many heavily edited images that i usually can't judge the creation well". First of, why would you make a judgement from its cover image, Its like looking at a book - You don't judge the book by its cover, You dwelve into the content. In this case, you download the creation and then you judge whether its good or not, don't you?

In conclusion, I hope you understand my clarification - If needs be I would be more than happy to discuss the matter further. Also, thanks for your personal preference as I believe this subject brings a good argument. In this case, a good idea for an article...