To shed some light on the situation, they did indeed have an obvious mistake in their comp point system, which apparently (according to hofdaddy) lasted for an entire week (I knew of the mistake but not the time period).
This mistake was, they were giving 4 comp points for every 1$ wagered, and they converted comp points to $ at the rate of 100 comp points for every $1. Obviously this is a 4% rebate, which is obviously a mistake, and it must have been especially obvious to the people complaining here.
Also, this happened during a transition in their comp points system. Before the mistake it was 4 points/$1 wagered, 4000 points to $1 cash, afterwards it was 1 point/$10 wagered, 100 points to convert to $1 cash. So you can see, they made a mistake (a really, really stupid mistake) in the transition.
This is open to debate, but in my mind they are within their rights to retroactively change the comp points to what they should have been, since this was an obvious error people were taking advantage of. However, voiding actual winnings and altering transaction histories is 100% unacceptable.
I think everyone here should put out in the open how much of their winnings was from gambling and how much was from comp points. I mean I understand there's another factor here of people getting lots of comp points and then using them to run up a huge balance where otherwise maybe they would have busted, so I guess any winnings generated purely with converted comp points could be taken back as well.
But when it's part converted comps and part their cash, I'd say the winnings have to be honored, and if someone just deposited, got the bonus, won money, converted their comps, then cashed out (which I feel is the majority situation here) then the winnings should be honored, minus the extra comps.