I don't know if it really factored into rustdoc's design since it was already built when I came to Rust, but when I was part of the team responsible for rustdoc, I did object to suggestions we do this on that basis.

As well as, extending the underlying language (that is, markdown) has to be done really carefully, and so being conservative with how it's done matters. This was a huge part of figuring out the design of intra-doc links in the first place.

(All of this great work is being done by others, and I don't know what their opinion on it really is, so my opinion being -1 doesn't really matter these days.)

Agreed, I find per-parameter docs useful in dynamic languages such as python, or to a lesser extent useful when the type system is weaker (in C), but in Rust I seldom find them useful. This can be useful to express constraints not present in the type system, for instance `fn matmul(a: Matrix<f64>, b: Matrix<f64>) -> Matrix<f64>` will benefit from a documentation describing the constraints and guarantees on the number of rows and cols of each matrix, since this cannot be expressed in the type system (yet).