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I agree that a chat/message feature is necessary. But encrypting messages on a public blockchain is extremely difficult, because you'd have to be sure that the encryption won't be broken in the next 20 or 50 years. I'd prefer a federated system that doesn't use the blockchain, but could be used on Steemit, Busy and other websits/apps.

There's @zappl, but I'm not sure whether it's working at the moment.