With the wonders of cryptography, you don't necessarily need to put secrets out in the open to notarize something on the blockchain. You can quite easily use a one way hash on the secret document, allowing you to verify the authenticity and the timestamp, but preventing someone from reversing the operation and seeing your secret information.

Turing completeness was sort of assumed with "Global computer". Neither myself nor the poster mentioned Ethereum at all. He just mentioned "global computer" as one application of blockchain that isn't a cryptocurrency. I could have just as easily been talking about NEO, which uses a number of languages, including C# and Java. Further, while Ethereum does frequently use a new language (Solidity), it doesn't rely on it. Ethereum is a virtual machine, and the first implementation of the virtual machine was Solidity. Others have been made as well, its turing complete after all.