@andreu seems to me like the old one should be completely ignored if the new one is present (regardless of order of appearance)
i believe that's how it works for standard scrollbar styling vs the older -webkit prefixed selectors; i use this example because it's closer to line-clamp than other prefixed properties in terms of behavioral difference
@mayank Huh, that is an interesting precedent that I didn't know about! But it's also a very different thing, because legacy selectors work very differently from the standard version.