the grey dots are not really a big problem. I would 'assume' from the data that these are just voting bots...but many of they combined may be making a good reward curating.
I would be more concerned about the accounts that are voting for 3-4 of these authors time and time again and no one else....and also not posting....hmmmm that might be something.....but it would also be down voted......
I just have a suspicious nature... the person(s) who controls those accounts may actually control thousands of accounts... like dust, you don't notice it, but if enough grains of sand are poured into a bucket owned by a single person?
It'll be interesting to see what comes up... seems you and @dwinblood might be able to really help each other out on this one.
perhaps they exploit the very information which you have uncovered. and yes, obviously many of the names on the voter list are quite similar