Stunna of course can see everyone's seeds. He can't manipulate your bets due to the way that the site's provably fair algorithm works. If he tried, he could be caught, and publicly outed. It's not worth the risk. The only real risk is that he could make an account and play on it knowing the seeds, and use the seeds to win. But he would only be winning from himself (and his private investors, assuming he has any). It's not a concern for players.
I am not a negativity person but suppose you do it right now . It means you can empty all of invested Clams in Just-Dice ?
Yes he can and so does the other site owner with the investment feature, they can play smartly and win from his own sites, because they know the seeds, this is a method use by hufflepuff to predict the next roll.
Although dooglus would not ruin his sites reputation by doing this .
he wouldn't ruin his site reputation by doing this... If he hides it more nobody will ever know. Maybe he did it already, nobody except dooglus knows that...