I took a quick look, and I'm no expert by a long shot.  I selected one of the 4.6 clam inputs, and that wallet had several 4.6 clam inputs, looking back at one of those, they came from the digger.  So it almost looks like the digger has several accounts on Poloniex.  That's one way around the withdrawal limits...    

   Depending on the system load on Poloniex, your deposit could be used to fund someones withdrawal, with out being merged into another address.  So just because you see a lot of 4.6 input's doesn't mean Poloniex is digging.  it only means Poloniex has a lot of clams broken up into 4.6 clam piles.  Which make sense since the digger is using Poloniex to unload.  


    This is not to say it could not be Poloniex, Just that based on them giving away clams in the beginning (via a dig???) and the fact the digger is using poloniex, makes it more unlikely.