This is in relation to #4470 custom-origin proposal (now in [Cascade 5](https://drafts.csswg.org/css-cascade-5/#layer-identifiers)), and the [Shadow DOM cascade rules](https://www.w3.org/TR/css-scoping-1/#shadow-cascading). To quote the original transcript: > emilio: Shadow DOM introduces a stack of origins; introducing this naively makes it a matrix, which is harder.