Sorry, I should have linked the re-rebalancing coherence RFC (that's just what it was called). I assumed that the reader of my message would be looking at the 1.41 release notes, where this can be easily found from the first thing linked.
No, it's not something you need to know about. All it did was just make the language easier to use by making more things work the way most users already expected them to.
(if, on the other hand, it's the phrase "cases where type parameters are allowed to appear in trait impls" that created confusion... yes, you might want to go read The Rust Programming Language, namely the section on Generics)