The only thing I remember about Secure Scuttlebutt is that it's anything but secure, but I can't for the life of me remember where I read it - can somebody jog my memory?
Edit: apart from that, nanomonkey is right, if you post something publicly, it will be public. That's to be expected though. And assuming the use of libsodium is done correctly, there shouldn't be much of a problem with the primitives.
Now, the logic implemented on top of the protocol is a whole different story, sort of like most ethereum cautionary tales are not about ethereum being buggy, but people running buggy code on ethereum.
If you know of other insecurities, I'd be interested in hearing them.