it looks like poloniex is digging for clams and also it sells it on the market. Imo this is a huge conflict of interests... Maybe they are the misterious digger.
Just curious if you can say what the conflict is? As I understand a conflict of interest, it's when someone has two (or more) competing financial interests: for example, say I am hired to regulate the oil industry in the name of the public interest and say I hold massive amounts of stock in that industry---here promoting either of my interests has a direct cost to the other. Or say, for a smaller scale example that I am paid to police the forums and mark scammers with negative trust and at the same time I sell accounts for a living---clearly neg-repping many accounts bumps the value the accounts I sell.
In your case, poloniex sells clams, so like any other clamholder they have an interest in getting a good price on the clam they sell. What's the conflict? What's the other interest?
It looks like there is not evidence to support this claim, but I wanted to add that margin trading is the biggest reason that any exchange trading on their own books is potentially a conflict of interest. In margin trading if you can see all the other traders' positions you have an advantage akin to being able to see everyone's hand in a game of poker. You can basically print money by knowing exactly how much it would take to make someone liquidate into your orders, or just direct the price slowly in your favor by taking the least crowded position.