I think you need to change "do the right thing" to "do what we say is the right thing". Presumably they don't agree that doing what you say is the right thing. Anyway, I'm not suggesting that you guys remove your negative feedback now, I'm suggesting that at some point in the future, if things continue to go fine with dadice (they offer their service, people use it, can withdrawl as needed) then it would seem that you'd admit that your warnings were unfounded and you'd remove the negative feedback. You'd say, "well they never proved their solvency to me but I guess they didn't really have to do that and it's been X (days/months/years/centuries) now and I guess I can safely remove this warning. " If that's right, I'm curious how long you think the warning should stand. What's the right value and unit for X?
I wonder how much your judgement is being coloured by wearing their signature. Or mine by being in competition with DaDice. I do know I have considered proof of solvency to be important for a long time, before I started Just-Dice, before I had such "competition".
Consider the situation: when asked about their solvency, they produced a string of feeble excuses for why they couldn't provide it. Once all these excuses were demonstrated to be feeble they would rather remove the investment feature from their site than prove solvency.
Ask yourself why they would do that. It makes them look guilty, when proving solvency would be so easy.
It strikes me that the only reason I wouldn't prove solvency in such a situation would be if I couldn't.
The warnings are there because they are a new site offering large bets with a small bankroll and are unwilling to prove that the bankroll exists. That's something worth warning about. The question of how long warnings should stay up for is a difficult one. I have scammers PMing me saying "it's been a year since I scammed, and I paid everyone back when I was caught, so can you remove the warning now?"... I don't remove it. They scammed once, they'll likely try it again. It doesn't matter that they've gone a year without scamming. If you had cause to believe MtGox was insolvent 2 years before they finally shut down, how long should you leave the warning up for? If they never prove their solvency, you have to reason to believe anything has changed.