CMON is different things to different people, and how it is used has changed over time. It started as a simple hot or not for miniature figurines. Over time, people started selling more painted figures on Ebay, and it became convenient to both buyers and sellers to link gallery images on CMON to active auctions on Ebay. That is of benefit to CMON, too, which earns money to keep the servers running by linking and featuring the auctions. Auction sellers have many times said they get far more views and bids on auctions when those auctions are linked to CMON gallery pages. I know at least a few auction sellers who detest CMON's ranking method and would be happy to avoid posting on the site if it didn't affect their sales.
A lot of people find the auction aspect of CMON very significant. For some, it's the only reason they use CMON. Others find it virtually irrelevant, a distraction from viewing figures and/or posting their own for feedback. I get the impression that some of the people upset about the situation fall into the latter group. The problem is there is just one way to post something on CMON, and just one type of gallery. It's happened on several occasions in the past that the owner of a painted miniature decides to sell it, and wanting to attract as many possible buyers wants to feature that sale on CMON. Usually the person credits the original painter either out of respect, or for simple salesmanship, since the painter is part of the sales appeal of a finely painted miniature. But unless the original painter is willing to feature the auction in their gallery, the seller has no choice but to post it in their own. That page is going to work the way every other page does and be up for votes. A lot of sellers take the pages down after the auction to minimize the effect on overall CMON ratings, but I don't think there are CMON rules requiring it, or even a moral obligation to do so.
Personally I consider it far less objectionable than the people who try to pad up their ratings or knock down someone else's with heavy trolling for votes on other forums or what-have-you. I've seen minis with hundreds more votes than others submited the same few days ago and other hints of similar things going on. A seller acknowledging the original painter is doing what they can to respect that painter and work within CMON as it functions. If someone searches the ratings and starts going through the gallery of that painter they'll soon realize that rating doesn't really apply to the gallery owner. If someone is concerned that they're ranked #597 instead of #572 because a few people were selling off collections of great minis, well that doesn't seem like such a big thing in the overall scheme of things to me.
As for a call for CMON to change and have display only galleries and whatnot, I suspect it's unlikely to happen. It's a relatively rare situation (which also applies to the Golden Toadstool account and probably a few others that have nothing to do with selling), and there's no workable way to apply it to all the pictures already posted. Stuff that can't be applied to the back catalogue rarely if ever is added. Crowd policing works pretty well, as keen eyes usually catch people who don't give credit for photos (as has happened here.) I suspect this particular person wasn't trying to claim credit for himself, but simply isn't familiar with the culture of the site and doesn't have great English. I further suspect he has very little familiarity with Ebay and miniature sales in general, since starting with whopper prices rarely seems to work, and crediting the skilled painters of his collection could only help his sales potential.
