[microtonal]

This may be true, but is not a very constructive comment without pointing out which language features or interactions between language features you find complex.

Ownership and the borrows checker may have a steep learning curve, but are not very complex. The rules are quite simple, the learning curve is steep because most programmers do not typically think about ownership (though they should).

(In my experience in teaching Rust, things like trait impl coherency rules, object safety, and finding a good balance between static and dynamic polymorphism are much harder for students than understanding the ownership system.)

[skywhopper]

Presumably the comment is not about Rust ownership rules, but about the language feature on display in the article: procedural macros.

[TheCoelacanth]

The are considerably simpler than the equivalent feature in C++ (template metaprogramming).