+1. From previous discussions (particularly Is sort() stable in Swift 5? - #11 by Ben_Cohen) the stability of the sort is de facto guaranteed already since changing the sort stability would essentially mean that sort behaves differently depending on target platform and that’s just not something that’s going to happen. This change clarifies that expectation without introducing any limitation with regards to future implementations of sorting algorithms with different attributes potentially requiring removing stability guarantees (since those can be provided as specific implementations with different APIs). I don't see any downside to this at all.