It looks like an interesting platform, but I was a bit surprised by what I found at:
https://developer.actor.im/docs/encryption
"MTProto v2 Rev3 enables encryption support to replace or enchanse TLS one." So far so good - here's someone that's built on top of NaCl and built a legacy-free encryption system on top of well tested, known primitives, I thought.
But: "Actor encrypts message with US encryption and then again encrypt with Russian encryption that in result guarantee absolute encryption streight" (sic).
Uh. This sounds like applying a "political" reasoning to layering security: AES might be backdoored by NSA, GOST(?) might be backdoored by the FSB -- but using both, only double-agents will be able to foil our encryption!
While the truth is probably that you're know vulnerable to buffer overflows or other more mundane software errors in the now double-sized encryption code -- and get none of the (potential) benefits of a clean, modern architecture on top of just NaCl?
In addition, it appears you also use curve25591, possibly an implementation derived from NaCl:
https://developer.actor.im/docs/securing-server
"For secure communications Actor Server have to be configured with Curve25519 keys. To generate them, use actor-cli util:"
So that's three codebases worth of bugs, rather than one. Any plan to simplify this part?