Hmm...I hear about it for the first time. I think it's some kind of a new startup but I don't believe for some reason that Bitcoin Diamond has relation to Bitcoin.
It seems Bitcoin Diamond has relation to Bitcoin because it share Bitcoin exact history up to block #495,866:
Bitcoin Diamond is a friendly dividend hard-fork of Bitcoin that is scheduled to happen at block #495,866
But at the end what matter is user support, so while Im very sceptical about Bitcoin Diamond, lets see what happens - privacy and fast transaction time might be usefull afterall.