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Regarding user experience, I think that every seed pair a user has made bets with should be stored in order to be able to verify previous bets of anyone at any time. Server seeds should automatically be revealed on each bet's page, thus, there would be no need for previous seed display at the provably fair tab.
Also, the bets table is refreshed live, which is a good idea, but ruins the experience if you want to check a specific bet: The user simply doesn't have enough time to click on the ID of a bet before it disappears. I think that the solution would be making the header of the table dock while the user is scrolling down, and as soon as the header has been docked, pause live refresh. When the user scrolls up above the header, making it undocked again, live refresh should be turned on again. (Similar behavior to PoloniBox).
Pagination for at least the "My bets" tab would also come handy. Finally, I think that besides the "High rollers" tab, there should be a "Reckless risktakers" (or similar) tab, showing profitable bets with a multiplier equal to or above 100x.