MicrostockGroup

When everything seems to be going well, @ SF there is a problem with the illustrations, especially with objects that has "Screen" blending mode: Preview file is not the same as in EPS which may mislead a client. (...)
To figure out what does this mean, I contacted the given e-mail and the response (I will not copy paste here because it isn't nice) told me that temporarily I should switch the document color mode into CMYK to check the document how it's looking. I was screaming and running up-down for 5 minutes then sitting down to figure out the proper response to this.
Intro: if you are familiar with the RGB-CMYK thing... Switching from RGB there is an another parameter coming in the game, so it's only a "figure-out" game, given by an icc profile. If the illustration contains complex blend modes, this is supposed to be rendered in the color space wit was designed. When switching the color space, the entire color set must be reworked. Sorry.
I was making this 6 years when preparing graphics for screen printing. No ICC profile on the world can handle RGB-CMYK conversion as the given technology wants (Screen, Flexo, Offset, etc.)

First at all, we are talking about this illustration:
ttp://www.dreamstime.com/sun-and-moon-in-yin-yang-symbol-image21532090
The moon is made of 3 objects that has "Screen" blend, 2 of them is going from pure black to a gray so this way the glow is made. When somebody converts the illustration into CMYK, the pure black is rendered as a dark gray (because in real printing there is no pure black so the ICC profile that converts the colors simulates this) so our "Screen" blend is rendered very ugly.
At SF, it's a part of the reviewing process to convert the document into CMYK and check what happens... (I'm running up-down again and screaming)
In short...
RGB illustrations should be verified in RGB mode, CMYK illustrations in CMYK mode!!!!! Any RGB-CMYK or CMYK-RGB conversion is LOSSY, there is a distortion of color data. Don't confuse photos with illustrations! Illustrations contain layers with specific blending modes. Converting the colors before FLATTENING the illustration results in a total mess...
I guess, this reviewing method was well going with EPS v8, where blending modes weren't working.

I prepared an answer but I'm afraid it's too long. Somebody pls. help me to answer in 2-3 phrases... It's just too much theory involved...

Generally I agree with you. If X agencies are happy with the same EPS10, there's no doubt about some glitch in the review process at SF.

But I still consider, feedback is important, this is how SF will figure out how the heck are there so many EPS's with incorrect preview files... 
I've sent an e-mail to the given address with comments and theories, let's see what's the answer.
I will post here the results...

If StockFresh wants to be that fair to buyers - we have to upload photographs as well in rgb and cmyk color space because some of these oversaturated bright rgb colors are very difficult, sometimes impossible to be converted.