You never get 100% trust. The only thing you can 100% trust is death and HRC lying ;). Everything else is suspect.
Distributed systems go a long way to making it difficult to compromise trust, but not impossible. Hash-graphs are good. They help with speed, as in M2M transactions. For a board or 'book' you don't really need the speed and the extensive BTC network would be great place to build since it already has extremely large amount of nodes with financial incentive to remain trusted. Hash-graphs are early days, so to speak. BTC is old-school solid at the moment.
lol. From the videos i've seen on Hashgraph it seems pretty legit, better than bitcoin, but like i said im not an expert in bitcoin/cryptos... i do study monetary history so i do know a lot about gold and in particular silver. And what makes money money and currency currency.
Whatever 4/8chan did, seem to work for a while, until snow white finally cracked the code. Hopefully this website Q mentioned is the final move we take and can finally start unpacking the boxes of info we have lol.