Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
visibility: visibleand non-
visibletransitions interpolate as
visibleapplies between 0–1; at and beyond 0/1 it clamps.
pseudoElementand the argument to
border-imagewith collapsed tables undefined, recommend not applying it to such tables in L3, expect it to be defined in L4.