> I love Rust, but one thing that seems like a glaring design flaw is that adding a new trait implementation can change the behavior of existing code. This is very counterintuitive, because it seems like a purely additive change.

> In my opinion, the convenience of auto-dereferencing "as much as possible" to make method call syntax magically work through the indirection of references is not worth the lack of stability guarantees that it causes.

Auto-deref is just one way of many that the dot operator can resolve to an unintended method. This problem would still exist even if auto-deref were removed. What you're really objecting to is the existence of the dot operator at all. I think the dot operator pulls its weight, given how often it's used: I encourage you to check out Simon Peyton-Jones' thoughts on "the power of the dot" [1].

[1]: https://www.microsoft.com/en-us/research/wp-content/uploads/...