https://www.reddit.com/r/rust/comments/34rszb/pony_type_and_...
https://www.wallaroo.ai/blog/wallaroo-move-to-rust
https://news.ycombinator.com/item?id=28777306
My sense is that Rust's constructs target more closely the mental schemas of individuals most concerned with memory safety; e.g., systems programming with lots of C, but wanting something more functional and safe.
I can see the comparisons between Pony and Rust, but I personally see them as kind of different in terms of who they might appeal to the most.
The liers are now thanksfully gone, but the compiler limitations are still there.