> Promises have always been extremely contentious in JS for a couple reasons and Domenic has had the patients of a saint getting the original proposal through so it's totally understandable that he might not want to deal with this anymore especially if people in his org are against it.

I know this is probably a typo (patients => patience) but that spelling seems to work as well.

> So cancelable promises reignite all the old debates plus there's no obvious right way to do it, like should it be a 3rd state which could cause compatibility issues and would add complexity, or should cancellations just be a sort of forced rejection, which would be a lot more backwards compatibility but with less features.

IMHO neither as cancelability isn't a common requirement. People that need it tend to have more complex requirements and end up tying the cancellation to other chains of logic anyway. Also, unlike say catching an error, you generally want all cancellation handlers to fire rather than just the first one (like with errors).