Now that you mention it, I do remember the backticks and symbols thing for infix, so yeah that’d be something extra that Haskell did. One of the few things about Haskell that wasn’t on the fringes of my capability and understanding as I recall.

I remember thinking that it would be cool if other, more procedural, languages allowed it, but then most other languages also don’t have the capability of setting the precedence of new operators relative to old ones on the fly. A lot of that stuff is hard-coded into those languages’ compilers.