Well said but I have a minor correction: #5 says the attachment is downloaded from the blockchain. This is incorrect. The attachments aren't on the blockchain, they're on IPFS.

"This means that your attachment is not stored on the blockchain but instead, an encrypted shadow copy is created on the IPFS. The shadow copy is stored on the IPFS but due to the complexities of the peer-to-peer network, there is no source to trace the transaction, so it is impossible to trace where or who the message was downloaded from or unscramble the separate hash to unlock your attachment."
Source: Ultranote Blog