If a picture element is given an opacity, the opacity is applied. However, if the picture element has a child img element that has display:block, the opacity isn't honoured unless the picture element has display:block as well. Expected behaviour: the opacity should be applied even with a display:block child. This affects Opera, Chrome and the latest version of Edge. It doesn't affect pre-webkit Edge and it doesn't affect Firefox. You can see this bug in this fiddle: https://jsfiddle.net/Skateside/k6zbeq1j/
The report doesn't explicitly mention WebKit, but I can reproduce in Safari indeed. Changing a behavior where we match Chrome can have negative compatibility effect of course.
<rdar://problem/71545258>