Coindice - the script that Paradice is built upon - generates the number fairly in the sense that it's randomly chosen and not biased. It's provably fair at the hash level - the player's roll is the same as the roll that the site provides the hash of - but it's not provably fair at the RNG level. The admin could theoretically edit the code so that it generates biased results and players wouldn't know or be able to do anything about it (due to the lack of a client seed). However, it's unlikely that Paradice (or any other site) would do anything like that - such a system implemented without great care could make a site more vulnerable to potential exploits - and I'm pretty sure there's no scam going on here, at least with the rolls. MafiaCoin's 'proof' post makes no sense - at best he just has no idea how it works, at worst he's just trying to cause trouble.
However, while it's unlikely that the site is cheating, personally I'd advise steering clear of paradice unless they implement a true provably fair system with a client seed option and rework their rules. A 'one account per user' rule on a Coindice-based site - where users are likely to accidentally create multiple accounts due to the automatic generation of them - is suspicious and could be used as an excuse to withhold legitimate withdrawals, and the same goes for a horribly vague rule like 'don't faucet farm' rather than having specific limitations on the use of the faucet.
I know how it works sha256-512 and provably fair!
I catch, he change seed. If use big amount, every bet lost and use fake seed.
Do you want try this shit provably system with bets 0.05btc and more?
I placed bets and he give fake seed.. After remove my account!
SHA of seed before bet and after is different!
SCAM